libceph: allow requests to return immediately on full conditions if caller wishes

[mirror_ubuntu-bionic-kernel.git] / fs / ceph / file.c

#include <linux/ceph/ceph_debug.h>

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/writeback.h>
#include <linux/falloc.h>

#include "super.h"
#include "mds_client.h"
#include "cache.h"

/*
 * Ceph file operations
 *
 * Implement basic open/close functionality, and implement
 * read/write.
 *
 * We implement three modes of file I/O:
 *  - buffered uses the generic_file_aio_{read,write} helpers
 *
 *  - synchronous is used when there is multi-client read/write
 *    sharing, avoids the page cache, and synchronously waits for an
 *    ack from the OSD.
 *
 *  - direct io takes the variant of the sync path that references
 *    user pages directly.
 *
 * fsync() flushes and waits on dirty pages, but just queues metadata
 * for writeback: since the MDS can recover size and mtime there is no
 * need to wait for MDS acknowledgement.
 */

/*
 * Calculate the length sum of direct io vectors that can
 * be combined into one page vector.
 */
static size_t dio_get_pagev_size(const struct iov_iter *it)
{
    const struct iovec *iov = it->iov;
    const struct iovec *iovend = iov + it->nr_segs;
    size_t size;

    size = iov->iov_len - it->iov_offset;
    /*
     * An iov can be page vectored when both the current tail
     * and the next base are page aligned.
     */
    while (PAGE_ALIGNED((iov->iov_base + iov->iov_len)) &&
           (++iov < iovend && PAGE_ALIGNED((iov->iov_base)))) {
        size += iov->iov_len;
    }
    dout("dio_get_pagevlen len = %zu\n", size);
    return size;
}

/*
 * Allocate a page vector based on (@it, @nbytes).
 * The return value is the tuple describing a page vector,
 * that is (@pages, @page_align, @num_pages).
 */
static struct page **
dio_get_pages_alloc(const struct iov_iter *it, size_t nbytes,
                    size_t *page_align, int *num_pages)
{
        struct iov_iter tmp_it = *it;
        size_t align;
        struct page **pages;
        int ret = 0, idx, npages;

        align = (unsigned long)(it->iov->iov_base + it->iov_offset) &
                (PAGE_SIZE - 1);
        npages = calc_pages_for(align, nbytes);
        pages = kmalloc(sizeof(*pages) * npages, GFP_KERNEL);
        if (!pages) {
                pages = vmalloc(sizeof(*pages) * npages);
                if (!pages)
                        return ERR_PTR(-ENOMEM);
        }

        for (idx = 0; idx < npages; ) {
                size_t start;
                ret = iov_iter_get_pages(&tmp_it, pages + idx, nbytes,
                                         npages - idx, &start);
                if (ret < 0)
                        goto fail;

                iov_iter_advance(&tmp_it, ret);
                nbytes -= ret;
                idx += (ret + start + PAGE_SIZE - 1) / PAGE_SIZE;
        }

        BUG_ON(nbytes != 0);
        *num_pages = npages;
        *page_align = align;
        dout("dio_get_pages_alloc: got %d pages align %zu\n", npages, align);
        return pages;
fail:
        ceph_put_page_vector(pages, idx, false);
        return ERR_PTR(ret);
}

/*
 * Prepare an open request.  Preallocate ceph_cap to avoid an
 * inopportune ENOMEM later.
 */
static struct ceph_mds_request *
prepare_open_request(struct super_block *sb, int flags, int create_mode)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int want_auth = USE_ANY_MDS;
        int op = (flags & O_CREAT) ? CEPH_MDS_OP_CREATE : CEPH_MDS_OP_OPEN;

        if (flags & (O_WRONLY|O_RDWR|O_CREAT|O_TRUNC))
                want_auth = USE_AUTH_MDS;

        req = ceph_mdsc_create_request(mdsc, op, want_auth);
        if (IS_ERR(req))
                goto out;
        req->r_fmode = ceph_flags_to_mode(flags);
        req->r_args.open.flags = cpu_to_le32(flags);
        req->r_args.open.mode = cpu_to_le32(create_mode);
out:
        return req;
}

/*
 * initialize private struct file data.
 * if we fail, clean up by dropping fmode reference on the ceph_inode
 */
static int ceph_init_file(struct inode *inode, struct file *file, int fmode)
{
        struct ceph_file_info *cf;
        int ret = 0;

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                ceph_fscache_register_inode_cookie(inode);
                ceph_fscache_file_set_cookie(inode, file);
        case S_IFDIR:
                dout("init_file %p %p 0%o (regular)\n", inode, file,
                     inode->i_mode);
                cf = kmem_cache_zalloc(ceph_file_cachep, GFP_KERNEL);
                if (cf == NULL) {
                        ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
                        return -ENOMEM;
                }
                cf->fmode = fmode;
                cf->next_offset = 2;
                cf->readdir_cache_idx = -1;
                file->private_data = cf;
                BUG_ON(inode->i_fop->release != ceph_release);
                break;

        case S_IFLNK:
                dout("init_file %p %p 0%o (symlink)\n", inode, file,
                     inode->i_mode);
                ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
                break;

        default:
                dout("init_file %p %p 0%o (special)\n", inode, file,
                     inode->i_mode);
                /*
                 * we need to drop the open ref now, since we don't
                 * have .release set to ceph_release.
                 */
                ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
                BUG_ON(inode->i_fop->release == ceph_release);

                /* call the proper open fop */
                ret = inode->i_fop->open(inode, file);
        }
        return ret;
}

/*
 * try renew caps after session gets killed.
 */
int ceph_renew_caps(struct inode *inode)
{
        struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_mds_request *req;
        int err, flags, wanted;

        spin_lock(&ci->i_ceph_lock);
        wanted = __ceph_caps_file_wanted(ci);
        if (__ceph_is_any_real_caps(ci) &&
            (!(wanted & CEPH_CAP_ANY_WR) || ci->i_auth_cap)) {
                int issued = __ceph_caps_issued(ci, NULL);
                spin_unlock(&ci->i_ceph_lock);
                dout("renew caps %p want %s issued %s updating mds_wanted\n",
                     inode, ceph_cap_string(wanted), ceph_cap_string(issued));
                ceph_check_caps(ci, 0, NULL);
                return 0;
        }
        spin_unlock(&ci->i_ceph_lock);

        flags = 0;
        if ((wanted & CEPH_CAP_FILE_RD) && (wanted & CEPH_CAP_FILE_WR))
                flags = O_RDWR;
        else if (wanted & CEPH_CAP_FILE_RD)
                flags = O_RDONLY;
        else if (wanted & CEPH_CAP_FILE_WR)
                flags = O_WRONLY;
#ifdef O_LAZY
        if (wanted & CEPH_CAP_FILE_LAZYIO)
                flags |= O_LAZY;
#endif

        req = prepare_open_request(inode->i_sb, flags, 0);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }

        req->r_inode = inode;
        ihold(inode);
        req->r_num_caps = 1;
        req->r_fmode = -1;

        err = ceph_mdsc_do_request(mdsc, NULL, req);
        ceph_mdsc_put_request(req);
out:
        dout("renew caps %p open result=%d\n", inode, err);
        return err < 0 ? err : 0;
}

/*
 * If we already have the requisite capabilities, we can satisfy
 * the open request locally (no need to request new caps from the
 * MDS).  We do, however, need to inform the MDS (asynchronously)
 * if our wanted caps set expands.
 */
int ceph_open(struct inode *inode, struct file *file)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_sb_to_client(inode->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        struct ceph_file_info *cf = file->private_data;
        int err;
        int flags, fmode, wanted;

        if (cf) {
                dout("open file %p is already opened\n", file);
                return 0;
        }

        /* filter out O_CREAT|O_EXCL; vfs did that already.  yuck. */
        flags = file->f_flags & ~(O_CREAT|O_EXCL);
        if (S_ISDIR(inode->i_mode))
                flags = O_DIRECTORY;  /* mds likes to know */

        dout("open inode %p ino %llx.%llx file %p flags %d (%d)\n", inode,
             ceph_vinop(inode), file, flags, file->f_flags);
        fmode = ceph_flags_to_mode(flags);
        wanted = ceph_caps_for_mode(fmode);

        /* snapped files are read-only */
        if (ceph_snap(inode) != CEPH_NOSNAP && (file->f_mode & FMODE_WRITE))
                return -EROFS;

        /* trivially open snapdir */
        if (ceph_snap(inode) == CEPH_SNAPDIR) {
                spin_lock(&ci->i_ceph_lock);
                __ceph_get_fmode(ci, fmode);
                spin_unlock(&ci->i_ceph_lock);
                return ceph_init_file(inode, file, fmode);
        }

        /*
         * No need to block if we have caps on the auth MDS (for
         * write) or any MDS (for read).  Update wanted set
         * asynchronously.
         */
        spin_lock(&ci->i_ceph_lock);
        if (__ceph_is_any_real_caps(ci) &&
            (((fmode & CEPH_FILE_MODE_WR) == 0) || ci->i_auth_cap)) {
                int mds_wanted = __ceph_caps_mds_wanted(ci, true);
                int issued = __ceph_caps_issued(ci, NULL);

                dout("open %p fmode %d want %s issued %s using existing\n",
                     inode, fmode, ceph_cap_string(wanted),
                     ceph_cap_string(issued));
                __ceph_get_fmode(ci, fmode);
                spin_unlock(&ci->i_ceph_lock);

                /* adjust wanted? */
                if ((issued & wanted) != wanted &&
                    (mds_wanted & wanted) != wanted &&
                    ceph_snap(inode) != CEPH_SNAPDIR)
                        ceph_check_caps(ci, 0, NULL);

                return ceph_init_file(inode, file, fmode);
        } else if (ceph_snap(inode) != CEPH_NOSNAP &&
                   (ci->i_snap_caps & wanted) == wanted) {
                __ceph_get_fmode(ci, fmode);
                spin_unlock(&ci->i_ceph_lock);
                return ceph_init_file(inode, file, fmode);
        }

        spin_unlock(&ci->i_ceph_lock);

        dout("open fmode %d wants %s\n", fmode, ceph_cap_string(wanted));
        req = prepare_open_request(inode->i_sb, flags, 0);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }
        req->r_inode = inode;
        ihold(inode);

        req->r_num_caps = 1;
        err = ceph_mdsc_do_request(mdsc, NULL, req);
        if (!err)
                err = ceph_init_file(inode, file, req->r_fmode);
        ceph_mdsc_put_request(req);
        dout("open result=%d on %llx.%llx\n", err, ceph_vinop(inode));
out:
        return err;
}


/*
 * Do a lookup + open with a single request.  If we get a non-existent
 * file or symlink, return 1 so the VFS can retry.
 */
int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
                     struct file *file, unsigned flags, umode_t mode,
                     int *opened)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        struct dentry *dn;
        struct ceph_acls_info acls = {};
       int mask;
        int err;

        dout("atomic_open %p dentry %p '%pd' %s flags %d mode 0%o\n",
             dir, dentry, dentry,
             d_unhashed(dentry) ? "unhashed" : "hashed", flags, mode);

        if (dentry->d_name.len > NAME_MAX)
                return -ENAMETOOLONG;

        if (flags & O_CREAT) {
                err = ceph_pre_init_acls(dir, &mode, &acls);
                if (err < 0)
                        return err;
        }

        /* do the open */
        req = prepare_open_request(dir->i_sb, flags, mode);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out_acl;
        }
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        if (flags & O_CREAT) {
                req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
                req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
                if (acls.pagelist) {
                        req->r_pagelist = acls.pagelist;
                        acls.pagelist = NULL;
                }
        }

       mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
       if (ceph_security_xattr_wanted(dir))
               mask |= CEPH_CAP_XATTR_SHARED;
       req->r_args.open.mask = cpu_to_le32(mask);

        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        err = ceph_mdsc_do_request(mdsc,
                                   (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
                                   req);
        err = ceph_handle_snapdir(req, dentry, err);
        if (err)
                goto out_req;

        if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
                err = ceph_handle_notrace_create(dir, dentry);

        if (d_in_lookup(dentry)) {
                dn = ceph_finish_lookup(req, dentry, err);
                if (IS_ERR(dn))
                        err = PTR_ERR(dn);
        } else {
                /* we were given a hashed negative dentry */
                dn = NULL;
        }
        if (err)
                goto out_req;
        if (dn || d_really_is_negative(dentry) || d_is_symlink(dentry)) {
                /* make vfs retry on splice, ENOENT, or symlink */
                dout("atomic_open finish_no_open on dn %p\n", dn);
                err = finish_no_open(file, dn);
        } else {
                dout("atomic_open finish_open on dn %p\n", dn);
                if (req->r_op == CEPH_MDS_OP_CREATE && req->r_reply_info.has_create_ino) {
                        ceph_init_inode_acls(d_inode(dentry), &acls);
                        *opened |= FILE_CREATED;
                }
                err = finish_open(file, dentry, ceph_open, opened);
        }
out_req:
        if (!req->r_err && req->r_target_inode)
                ceph_put_fmode(ceph_inode(req->r_target_inode), req->r_fmode);
        ceph_mdsc_put_request(req);
out_acl:
        ceph_release_acls_info(&acls);
        dout("atomic_open result=%d\n", err);
        return err;
}

int ceph_release(struct inode *inode, struct file *file)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_file_info *cf = file->private_data;

        dout("release inode %p file %p\n", inode, file);
        ceph_put_fmode(ci, cf->fmode);
        if (cf->last_readdir)
                ceph_mdsc_put_request(cf->last_readdir);
        kfree(cf->last_name);
        kfree(cf->dir_info);
        kmem_cache_free(ceph_file_cachep, cf);

        /* wake up anyone waiting for caps on this inode */
        wake_up_all(&ci->i_cap_wq);
        return 0;
}

enum {
        HAVE_RETRIED = 1,
        CHECK_EOF =    2,
        READ_INLINE =  3,
};

/*
 * Read a range of bytes striped over one or more objects.  Iterate over
 * objects we stripe over.  (That's not atomic, but good enough for now.)
 *
 * If we get a short result from the OSD, check against i_size; we need to
 * only return a short read to the caller if we hit EOF.
 */
static int striped_read(struct inode *inode,
                        u64 pos, u64 len,
                        struct page **pages, int num_pages,
                        int page_align, int *checkeof)
{
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        u64 this_len;
        loff_t i_size;
        int page_idx;
        int ret, read = 0;
        bool hit_stripe, was_short;

        /*
         * we may need to do multiple reads.  not atomic, unfortunately.
         */
more:
        this_len = len;
        page_idx = (page_align + read) >> PAGE_SHIFT;
        ret = ceph_osdc_readpages(&fsc->client->osdc, ceph_vino(inode),
                                  &ci->i_layout, pos, &this_len,
                                  ci->i_truncate_seq, ci->i_truncate_size,
                                  pages + page_idx, num_pages - page_idx,
                                  ((page_align + read) & ~PAGE_MASK));
        if (ret == -ENOENT)
                ret = 0;
        hit_stripe = this_len < len;
        was_short = ret >= 0 && ret < this_len;
        dout("striped_read %llu~%llu (read %u) got %d%s%s\n", pos, len, read,
             ret, hit_stripe ? " HITSTRIPE" : "", was_short ? " SHORT" : "");

        i_size = i_size_read(inode);
        if (ret >= 0) {
                if (was_short && (pos + ret < i_size)) {
                        int zlen = min(this_len - ret, i_size - pos - ret);
                        int zoff = page_align + read + ret;
                        dout(" zero gap %llu to %llu\n",
                             pos + ret, pos + ret + zlen);
                        ceph_zero_page_vector_range(zoff, zlen, pages);
                        ret += zlen;
                }

                read += ret;
                pos += ret;
                len -= ret;

                /* hit stripe and need continue*/
                if (len && hit_stripe && pos < i_size)
                        goto more;
        }

        if (read > 0) {
                ret = read;
                /* did we bounce off eof? */
                if (pos + len > i_size)
                        *checkeof = CHECK_EOF;
        }

        dout("striped_read returns %d\n", ret);
        return ret;
}

/*
 * Completely synchronous read and write methods.  Direct from __user
 * buffer to osd, or directly to user pages (if O_DIRECT).
 *
 * If the read spans object boundary, just do multiple reads.
 */
static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *to,
                              int *checkeof)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct page **pages;
        u64 off = iocb->ki_pos;
        int num_pages;
        ssize_t ret;
        size_t len = iov_iter_count(to);

        dout("sync_read on file %p %llu~%u %s\n", file, off,
             (unsigned)len,
             (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");

        if (!len)
                return 0;
        /*
         * flush any page cache pages in this range.  this
         * will make concurrent normal and sync io slow,
         * but it will at least behave sensibly when they are
         * in sequence.
         */
        ret = filemap_write_and_wait_range(inode->i_mapping, off,
                                                off + len);
        if (ret < 0)
                return ret;

        if (unlikely(to->type & ITER_PIPE)) {
                size_t page_off;
                ret = iov_iter_get_pages_alloc(to, &pages, len,
                                               &page_off);
                if (ret <= 0)
                        return -ENOMEM;
                num_pages = DIV_ROUND_UP(ret + page_off, PAGE_SIZE);

                ret = striped_read(inode, off, ret, pages, num_pages,
                                   page_off, checkeof);
                if (ret > 0) {
                        iov_iter_advance(to, ret);
                        off += ret;
                } else {
                        iov_iter_advance(to, 0);
                }
                ceph_put_page_vector(pages, num_pages, false);
        } else {
                num_pages = calc_pages_for(off, len);
                pages = ceph_alloc_page_vector(num_pages, GFP_KERNEL);
                if (IS_ERR(pages))
                        return PTR_ERR(pages);

                ret = striped_read(inode, off, len, pages, num_pages,
                                   (off & ~PAGE_MASK), checkeof);
                if (ret > 0) {
                        int l, k = 0;
                        size_t left = ret;

                        while (left) {
                                size_t page_off = off & ~PAGE_MASK;
                                size_t copy = min_t(size_t, left,
                                                    PAGE_SIZE - page_off);
                                l = copy_page_to_iter(pages[k++], page_off,
                                                      copy, to);
                                off += l;
                                left -= l;
                                if (l < copy)
                                        break;
                        }
                }
                ceph_release_page_vector(pages, num_pages);
        }

        if (off > iocb->ki_pos) {
                ret = off - iocb->ki_pos;
                iocb->ki_pos = off;
        }

        dout("sync_read result %zd\n", ret);
        return ret;
}

struct ceph_aio_request {
        struct kiocb *iocb;
        size_t total_len;
        int write;
        int error;
        struct list_head osd_reqs;
        unsigned num_reqs;
        atomic_t pending_reqs;
        struct timespec mtime;
        struct ceph_cap_flush *prealloc_cf;
};

struct ceph_aio_work {
        struct work_struct work;
        struct ceph_osd_request *req;
};

static void ceph_aio_retry_work(struct work_struct *work);

static void ceph_aio_complete(struct inode *inode,
                              struct ceph_aio_request *aio_req)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        int ret;

        if (!atomic_dec_and_test(&aio_req->pending_reqs))
                return;

        ret = aio_req->error;
        if (!ret)
                ret = aio_req->total_len;

        dout("ceph_aio_complete %p rc %d\n", inode, ret);

        if (ret >= 0 && aio_req->write) {
                int dirty;

                loff_t endoff = aio_req->iocb->ki_pos + aio_req->total_len;
                if (endoff > i_size_read(inode)) {
                        if (ceph_inode_set_size(inode, endoff))
                                ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
                }

                spin_lock(&ci->i_ceph_lock);
                ci->i_inline_version = CEPH_INLINE_NONE;
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
                                               &aio_req->prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);

        }

        ceph_put_cap_refs(ci, (aio_req->write ? CEPH_CAP_FILE_WR :
                                                CEPH_CAP_FILE_RD));

        aio_req->iocb->ki_complete(aio_req->iocb, ret, 0);

        ceph_free_cap_flush(aio_req->prealloc_cf);
        kfree(aio_req);
}

static void ceph_aio_complete_req(struct ceph_osd_request *req)
{
        int rc = req->r_result;
        struct inode *inode = req->r_inode;
        struct ceph_aio_request *aio_req = req->r_priv;
        struct ceph_osd_data *osd_data = osd_req_op_extent_osd_data(req, 0);
        int num_pages = calc_pages_for((u64)osd_data->alignment,
                                       osd_data->length);

        dout("ceph_aio_complete_req %p rc %d bytes %llu\n",
             inode, rc, osd_data->length);

        if (rc == -EOLDSNAPC) {
                struct ceph_aio_work *aio_work;
                BUG_ON(!aio_req->write);

                aio_work = kmalloc(sizeof(*aio_work), GFP_NOFS);
                if (aio_work) {
                        INIT_WORK(&aio_work->work, ceph_aio_retry_work);
                        aio_work->req = req;
                        queue_work(ceph_inode_to_client(inode)->wb_wq,
                                   &aio_work->work);
                        return;
                }
                rc = -ENOMEM;
        } else if (!aio_req->write) {
                if (rc == -ENOENT)
                        rc = 0;
                if (rc >= 0 && osd_data->length > rc) {
                        int zoff = osd_data->alignment + rc;
                        int zlen = osd_data->length - rc;
                        /*
                         * If read is satisfied by single OSD request,
                         * it can pass EOF. Otherwise read is within
                         * i_size.
                         */
                        if (aio_req->num_reqs == 1) {
                                loff_t i_size = i_size_read(inode);
                                loff_t endoff = aio_req->iocb->ki_pos + rc;
                                if (endoff < i_size)
                                        zlen = min_t(size_t, zlen,
                                                     i_size - endoff);
                                aio_req->total_len = rc + zlen;
                        }

                        if (zlen > 0)
                                ceph_zero_page_vector_range(zoff, zlen,
                                                            osd_data->pages);
                }
        }

        ceph_put_page_vector(osd_data->pages, num_pages, !aio_req->write);
        ceph_osdc_put_request(req);

        if (rc < 0)
                cmpxchg(&aio_req->error, 0, rc);

        ceph_aio_complete(inode, aio_req);
        return;
}

static void ceph_aio_retry_work(struct work_struct *work)
{
        struct ceph_aio_work *aio_work =
                container_of(work, struct ceph_aio_work, work);
        struct ceph_osd_request *orig_req = aio_work->req;
        struct ceph_aio_request *aio_req = orig_req->r_priv;
        struct inode *inode = orig_req->r_inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc;
        struct ceph_osd_request *req;
        int ret;

        spin_lock(&ci->i_ceph_lock);
        if (__ceph_have_pending_cap_snap(ci)) {
                struct ceph_cap_snap *capsnap =
                        list_last_entry(&ci->i_cap_snaps,
                                        struct ceph_cap_snap,
                                        ci_item);
                snapc = ceph_get_snap_context(capsnap->context);
        } else {
                BUG_ON(!ci->i_head_snapc);
                snapc = ceph_get_snap_context(ci->i_head_snapc);
        }
        spin_unlock(&ci->i_ceph_lock);

        req = ceph_osdc_alloc_request(orig_req->r_osdc, snapc, 2,
                        false, GFP_NOFS);
        if (!req) {
                ret = -ENOMEM;
                req = orig_req;
                goto out;
        }

        req->r_flags = CEPH_OSD_FLAG_ORDERSNAP | CEPH_OSD_FLAG_WRITE;
        ceph_oloc_copy(&req->r_base_oloc, &orig_req->r_base_oloc);
        ceph_oid_copy(&req->r_base_oid, &orig_req->r_base_oid);

        ret = ceph_osdc_alloc_messages(req, GFP_NOFS);
        if (ret) {
                ceph_osdc_put_request(req);
                req = orig_req;
                goto out;
        }

        req->r_ops[0] = orig_req->r_ops[0];
        osd_req_op_init(req, 1, CEPH_OSD_OP_STARTSYNC, 0);

        req->r_mtime = aio_req->mtime;
        req->r_data_offset = req->r_ops[0].extent.offset;

        ceph_osdc_put_request(orig_req);

        req->r_callback = ceph_aio_complete_req;
        req->r_inode = inode;
        req->r_priv = aio_req;
        req->r_abort_on_full = true;

        ret = ceph_osdc_start_request(req->r_osdc, req, false);
out:
        if (ret < 0) {
                req->r_result = ret;
                ceph_aio_complete_req(req);
        }

        ceph_put_snap_context(snapc);
        kfree(aio_work);
}

static ssize_t
ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter,
                       struct ceph_snap_context *snapc,
                       struct ceph_cap_flush **pcf)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_vino vino;
        struct ceph_osd_request *req;
        struct page **pages;
        struct ceph_aio_request *aio_req = NULL;
        int num_pages = 0;
        int flags;
        int ret;
        struct timespec mtime = current_time(inode);
        size_t count = iov_iter_count(iter);
        loff_t pos = iocb->ki_pos;
        bool write = iov_iter_rw(iter) == WRITE;

        if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
                return -EROFS;

        dout("sync_direct_read_write (%s) on file %p %lld~%u\n",
             (write ? "write" : "read"), file, pos, (unsigned)count);

        ret = filemap_write_and_wait_range(inode->i_mapping, pos, pos + count);
        if (ret < 0)
                return ret;

        if (write) {
                int ret2 = invalidate_inode_pages2_range(inode->i_mapping,
                                        pos >> PAGE_SHIFT,
                                        (pos + count) >> PAGE_SHIFT);
                if (ret2 < 0)
                        dout("invalidate_inode_pages2_range returned %d\n", ret2);

                flags = CEPH_OSD_FLAG_ORDERSNAP | CEPH_OSD_FLAG_WRITE;
        } else {
                flags = CEPH_OSD_FLAG_READ;
        }

        while (iov_iter_count(iter) > 0) {
                u64 size = dio_get_pagev_size(iter);
                size_t start = 0;
                ssize_t len;

                vino = ceph_vino(inode);
                req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                            vino, pos, &size, 0,
                                            /*include a 'startsync' command*/
                                            write ? 2 : 1,
                                            write ? CEPH_OSD_OP_WRITE :
                                                    CEPH_OSD_OP_READ,
                                            flags, snapc,
                                            ci->i_truncate_seq,
                                            ci->i_truncate_size,
                                            false);
                if (IS_ERR(req)) {
                        ret = PTR_ERR(req);
                        break;
                }

                len = size;
                pages = dio_get_pages_alloc(iter, len, &start, &num_pages);
                if (IS_ERR(pages)) {
                        ceph_osdc_put_request(req);
                        ret = PTR_ERR(pages);
                        break;
                }

                /*
                 * To simplify error handling, allow AIO when IO within i_size
                 * or IO can be satisfied by single OSD request.
                 */
                if (pos == iocb->ki_pos && !is_sync_kiocb(iocb) &&
                    (len == count || pos + count <= i_size_read(inode))) {
                        aio_req = kzalloc(sizeof(*aio_req), GFP_KERNEL);
                        if (aio_req) {
                                aio_req->iocb = iocb;
                                aio_req->write = write;
                                INIT_LIST_HEAD(&aio_req->osd_reqs);
                                if (write) {
                                        aio_req->mtime = mtime;
                                        swap(aio_req->prealloc_cf, *pcf);
                                }
                        }
                        /* ignore error */
                }

                if (write) {
                        /*
                         * throw out any page cache pages in this range. this
                         * may block.
                         */
                        truncate_inode_pages_range(inode->i_mapping, pos,
                                        (pos+len) | (PAGE_SIZE - 1));

                        osd_req_op_init(req, 1, CEPH_OSD_OP_STARTSYNC, 0);
                        req->r_mtime = mtime;
                }

                osd_req_op_extent_osd_data_pages(req, 0, pages, len, start,
                                                 false, false);

                if (aio_req) {
                        aio_req->total_len += len;
                        aio_req->num_reqs++;
                        atomic_inc(&aio_req->pending_reqs);

                        req->r_callback = ceph_aio_complete_req;
                        req->r_inode = inode;
                        req->r_priv = aio_req;
                        list_add_tail(&req->r_unsafe_item, &aio_req->osd_reqs);

                        pos += len;
                        iov_iter_advance(iter, len);
                        continue;
                }

                ret = ceph_osdc_start_request(req->r_osdc, req, false);
                if (!ret)
                        ret = ceph_osdc_wait_request(&fsc->client->osdc, req);

                size = i_size_read(inode);
                if (!write) {
                        if (ret == -ENOENT)
                                ret = 0;
                        if (ret >= 0 && ret < len && pos + ret < size) {
                                int zlen = min_t(size_t, len - ret,
                                                 size - pos - ret);
                                ceph_zero_page_vector_range(start + ret, zlen,
                                                            pages);
                                ret += zlen;
                        }
                        if (ret >= 0)
                                len = ret;
                }

                ceph_put_page_vector(pages, num_pages, !write);

                ceph_osdc_put_request(req);
                if (ret < 0)
                        break;

                pos += len;
                iov_iter_advance(iter, len);

                if (!write && pos >= size)
                        break;

                if (write && pos > size) {
                        if (ceph_inode_set_size(inode, pos))
                                ceph_check_caps(ceph_inode(inode),
                                                CHECK_CAPS_AUTHONLY,
                                                NULL);
                }
        }

        if (aio_req) {
                LIST_HEAD(osd_reqs);

                if (aio_req->num_reqs == 0) {
                        kfree(aio_req);
                        return ret;
                }

                ceph_get_cap_refs(ci, write ? CEPH_CAP_FILE_WR :
                                              CEPH_CAP_FILE_RD);

                list_splice(&aio_req->osd_reqs, &osd_reqs);
                while (!list_empty(&osd_reqs)) {
                        req = list_first_entry(&osd_reqs,
                                               struct ceph_osd_request,
                                               r_unsafe_item);
                        list_del_init(&req->r_unsafe_item);
                        if (ret >= 0)
                                ret = ceph_osdc_start_request(req->r_osdc,
                                                              req, false);
                        if (ret < 0) {
                                req->r_result = ret;
                                ceph_aio_complete_req(req);
                        }
                }
                return -EIOCBQUEUED;
        }

        if (ret != -EOLDSNAPC && pos > iocb->ki_pos) {
                ret = pos - iocb->ki_pos;
                iocb->ki_pos = pos;
        }
        return ret;
}

/*
 * Synchronous write, straight from __user pointer or user pages.
 *
 * If write spans object boundary, just do multiple writes.  (For a
 * correct atomic write, we should e.g. take write locks on all
 * objects, rollback on failure, etc.)
 */
static ssize_t
ceph_sync_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos,
                struct ceph_snap_context *snapc)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_vino vino;
        struct ceph_osd_request *req;
        struct page **pages;
        u64 len;
        int num_pages;
        int written = 0;
        int flags;
        int check_caps = 0;
        int ret;
        struct timespec mtime = current_time(inode);
        size_t count = iov_iter_count(from);

        if (ceph_snap(file_inode(file)) != CEPH_NOSNAP)
                return -EROFS;

        dout("sync_write on file %p %lld~%u\n", file, pos, (unsigned)count);

        ret = filemap_write_and_wait_range(inode->i_mapping, pos, pos + count);
        if (ret < 0)
                return ret;

        ret = invalidate_inode_pages2_range(inode->i_mapping,
                                            pos >> PAGE_SHIFT,
                                            (pos + count) >> PAGE_SHIFT);
        if (ret < 0)
                dout("invalidate_inode_pages2_range returned %d\n", ret);

        flags = CEPH_OSD_FLAG_ORDERSNAP | CEPH_OSD_FLAG_WRITE;

        while ((len = iov_iter_count(from)) > 0) {
                size_t left;
                int n;

                vino = ceph_vino(inode);
                req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                            vino, pos, &len, 0, 1,
                                            CEPH_OSD_OP_WRITE, flags, snapc,
                                            ci->i_truncate_seq,
                                            ci->i_truncate_size,
                                            false);
                if (IS_ERR(req)) {
                        ret = PTR_ERR(req);
                        break;
                }

                /*
                 * write from beginning of first page,
                 * regardless of io alignment
                 */
                num_pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;

                pages = ceph_alloc_page_vector(num_pages, GFP_KERNEL);
                if (IS_ERR(pages)) {
                        ret = PTR_ERR(pages);
                        goto out;
                }

                left = len;
                for (n = 0; n < num_pages; n++) {
                        size_t plen = min_t(size_t, left, PAGE_SIZE);
                        ret = copy_page_from_iter(pages[n], 0, plen, from);
                        if (ret != plen) {
                                ret = -EFAULT;
                                break;
                        }
                        left -= ret;
                }

                if (ret < 0) {
                        ceph_release_page_vector(pages, num_pages);
                        goto out;
                }

                req->r_inode = inode;

                osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0,
                                                false, true);

                req->r_mtime = mtime;
                ret = ceph_osdc_start_request(&fsc->client->osdc, req, false);
                if (!ret)
                        ret = ceph_osdc_wait_request(&fsc->client->osdc, req);

out:
                ceph_osdc_put_request(req);
                if (ret == 0) {
                        pos += len;
                        written += len;

                        if (pos > i_size_read(inode)) {
                                check_caps = ceph_inode_set_size(inode, pos);
                                if (check_caps)
                                        ceph_check_caps(ceph_inode(inode),
                                                        CHECK_CAPS_AUTHONLY,
                                                        NULL);
                        }
                } else
                        break;
        }

        if (ret != -EOLDSNAPC && written > 0) {
                ret = written;
                iocb->ki_pos = pos;
        }
        return ret;
}

/*
 * Wrap generic_file_aio_read with checks for cap bits on the inode.
 * Atomically grab references, so that those bits are not released
 * back to the MDS mid-read.
 *
 * Hmm, the sync read case isn't actually async... should it be?
 */
static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *filp = iocb->ki_filp;
        struct ceph_file_info *fi = filp->private_data;
        size_t len = iov_iter_count(to);
        struct inode *inode = file_inode(filp);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct page *pinned_page = NULL;
        ssize_t ret;
        int want, got = 0;
        int retry_op = 0, read = 0;

again:
        dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
             inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len, inode);

        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_CACHE;
        ret = ceph_get_caps(ci, CEPH_CAP_FILE_RD, want, -1, &got, &pinned_page);
        if (ret < 0)
                return ret;

        if ((got & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0 ||
            (iocb->ki_flags & IOCB_DIRECT) ||
            (fi->flags & CEPH_F_SYNC)) {

                dout("aio_sync_read %p %llx.%llx %llu~%u got cap refs on %s\n",
                     inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
                     ceph_cap_string(got));

                if (ci->i_inline_version == CEPH_INLINE_NONE) {
                        if (!retry_op && (iocb->ki_flags & IOCB_DIRECT)) {
                                ret = ceph_direct_read_write(iocb, to,
                                                             NULL, NULL);
                                if (ret >= 0 && ret < len)
                                        retry_op = CHECK_EOF;
                        } else {
                                ret = ceph_sync_read(iocb, to, &retry_op);
                        }
                } else {
                        retry_op = READ_INLINE;
                }
        } else {
                dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
                     inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
                     ceph_cap_string(got));
                current->journal_info = filp;
                ret = generic_file_read_iter(iocb, to);
                current->journal_info = NULL;
        }
        dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
             inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
        if (pinned_page) {
                put_page(pinned_page);
                pinned_page = NULL;
        }
        ceph_put_cap_refs(ci, got);
        if (retry_op > HAVE_RETRIED && ret >= 0) {
                int statret;
                struct page *page = NULL;
                loff_t i_size;
                if (retry_op == READ_INLINE) {
                        page = __page_cache_alloc(GFP_KERNEL);
                        if (!page)
                                return -ENOMEM;
                }

                statret = __ceph_do_getattr(inode, page,
                                            CEPH_STAT_CAP_INLINE_DATA, !!page);
                if (statret < 0) {
                        if (page)
                                __free_page(page);
                        if (statret == -ENODATA) {
                                BUG_ON(retry_op != READ_INLINE);
                                goto again;
                        }
                        return statret;
                }

                i_size = i_size_read(inode);
                if (retry_op == READ_INLINE) {
                        BUG_ON(ret > 0 || read > 0);
                        if (iocb->ki_pos < i_size &&
                            iocb->ki_pos < PAGE_SIZE) {
                                loff_t end = min_t(loff_t, i_size,
                                                   iocb->ki_pos + len);
                                end = min_t(loff_t, end, PAGE_SIZE);
                                if (statret < end)
                                        zero_user_segment(page, statret, end);
                                ret = copy_page_to_iter(page,
                                                iocb->ki_pos & ~PAGE_MASK,
                                                end - iocb->ki_pos, to);
                                iocb->ki_pos += ret;
                                read += ret;
                        }
                        if (iocb->ki_pos < i_size && read < len) {
                                size_t zlen = min_t(size_t, len - read,
                                                    i_size - iocb->ki_pos);
                                ret = iov_iter_zero(zlen, to);
                                iocb->ki_pos += ret;
                                read += ret;
                        }
                        __free_pages(page, 0);
                        return read;
                }

                /* hit EOF or hole? */
                if (retry_op == CHECK_EOF && iocb->ki_pos < i_size &&
                    ret < len) {
                        dout("sync_read hit hole, ppos %lld < size %lld"
                             ", reading more\n", iocb->ki_pos, i_size);

                        read += ret;
                        len -= ret;
                        retry_op = HAVE_RETRIED;
                        goto again;
                }
        }

        if (ret >= 0)
                ret += read;

        return ret;
}

/*
 * Take cap references to avoid releasing caps to MDS mid-write.
 *
 * If we are synchronous, and write with an old snap context, the OSD
 * may return EOLDSNAPC.  In that case, retry the write.. _after_
 * dropping our cap refs and allowing the pending snap to logically
 * complete _before_ this write occurs.
 *
 * If we are near ENOSPC, write synchronously.
 */
static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct ceph_file_info *fi = file->private_data;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_osd_client *osdc =
                &ceph_sb_to_client(inode->i_sb)->client->osdc;
        struct ceph_cap_flush *prealloc_cf;
        ssize_t count, written = 0;
        int err, want, got;
        loff_t pos;

        if (ceph_snap(inode) != CEPH_NOSNAP)
                return -EROFS;

        prealloc_cf = ceph_alloc_cap_flush();
        if (!prealloc_cf)
                return -ENOMEM;

        inode_lock(inode);

        /* We can write back this queue in page reclaim */
        current->backing_dev_info = inode_to_bdi(inode);

        if (iocb->ki_flags & IOCB_APPEND) {
                err = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
                if (err < 0)
                        goto out;
        }

        err = generic_write_checks(iocb, from);
        if (err <= 0)
                goto out;

        pos = iocb->ki_pos;
        count = iov_iter_count(from);
        err = file_remove_privs(file);
        if (err)
                goto out;

        err = file_update_time(file);
        if (err)
                goto out;

        if (ci->i_inline_version != CEPH_INLINE_NONE) {
                err = ceph_uninline_data(file, NULL);
                if (err < 0)
                        goto out;
        }

retry_snap:
        if (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL)) {
                err = -ENOSPC;
                goto out;
        }

        dout("aio_write %p %llx.%llx %llu~%zd getting caps. i_size %llu\n",
             inode, ceph_vinop(inode), pos, count, i_size_read(inode));
        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_BUFFER;
        got = 0;
        err = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, pos + count,
                            &got, NULL);
        if (err < 0)
                goto out;

        dout("aio_write %p %llx.%llx %llu~%zd got cap refs on %s\n",
             inode, ceph_vinop(inode), pos, count, ceph_cap_string(got));

        if ((got & (CEPH_CAP_FILE_BUFFER|CEPH_CAP_FILE_LAZYIO)) == 0 ||
            (iocb->ki_flags & IOCB_DIRECT) || (fi->flags & CEPH_F_SYNC)) {
                struct ceph_snap_context *snapc;
                struct iov_iter data;
                inode_unlock(inode);

                spin_lock(&ci->i_ceph_lock);
                if (__ceph_have_pending_cap_snap(ci)) {
                        struct ceph_cap_snap *capsnap =
                                        list_last_entry(&ci->i_cap_snaps,
                                                        struct ceph_cap_snap,
                                                        ci_item);
                        snapc = ceph_get_snap_context(capsnap->context);
                } else {
                        BUG_ON(!ci->i_head_snapc);
                        snapc = ceph_get_snap_context(ci->i_head_snapc);
                }
                spin_unlock(&ci->i_ceph_lock);

                /* we might need to revert back to that point */
                data = *from;
                if (iocb->ki_flags & IOCB_DIRECT)
                        written = ceph_direct_read_write(iocb, &data, snapc,
                                                         &prealloc_cf);
                else
                        written = ceph_sync_write(iocb, &data, pos, snapc);
                if (written == -EOLDSNAPC) {
                        dout("aio_write %p %llx.%llx %llu~%u"
                                "got EOLDSNAPC, retrying\n",
                                inode, ceph_vinop(inode),
                                pos, (unsigned)count);
                        inode_lock(inode);
                        goto retry_snap;
                }
                if (written > 0)
                        iov_iter_advance(from, written);
                ceph_put_snap_context(snapc);
        } else {
                /*
                 * No need to acquire the i_truncate_mutex. Because
                 * the MDS revokes Fwb caps before sending truncate
                 * message to us. We can't get Fwb cap while there
                 * are pending vmtruncate. So write and vmtruncate
                 * can not run at the same time
                 */
                written = generic_perform_write(file, from, pos);
                if (likely(written >= 0))
                        iocb->ki_pos = pos + written;
                inode_unlock(inode);
        }

        if (written >= 0) {
                int dirty;
                spin_lock(&ci->i_ceph_lock);
                ci->i_inline_version = CEPH_INLINE_NONE;
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
                                               &prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);
        }

        dout("aio_write %p %llx.%llx %llu~%u  dropping cap refs on %s\n",
             inode, ceph_vinop(inode), pos, (unsigned)count,
             ceph_cap_string(got));
        ceph_put_cap_refs(ci, got);

        if (written >= 0) {
                if (ceph_osdmap_flag(osdc, CEPH_OSDMAP_NEARFULL))
                        iocb->ki_flags |= IOCB_DSYNC;

                written = generic_write_sync(iocb, written);
        }

        goto out_unlocked;

out:
        inode_unlock(inode);
out_unlocked:
        ceph_free_cap_flush(prealloc_cf);
        current->backing_dev_info = NULL;
        return written ? written : err;
}

/*
 * llseek.  be sure to verify file size on SEEK_END.
 */
static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file->f_mapping->host;
        loff_t i_size;
        loff_t ret;

        inode_lock(inode);

        if (whence == SEEK_END || whence == SEEK_DATA || whence == SEEK_HOLE) {
                ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
                if (ret < 0)
                        goto out;
        }

        i_size = i_size_read(inode);
        switch (whence) {
        case SEEK_END:
                offset += i_size;
                break;
        case SEEK_CUR:
                /*
                 * Here we special-case the lseek(fd, 0, SEEK_CUR)
                 * position-querying operation.  Avoid rewriting the "same"
                 * f_pos value back to the file because a concurrent read(),
                 * write() or lseek() might have altered it
                 */
                if (offset == 0) {
                        ret = file->f_pos;
                        goto out;
                }
                offset += file->f_pos;
                break;
        case SEEK_DATA:
                if (offset >= i_size) {
                        ret = -ENXIO;
                        goto out;
                }
                break;
        case SEEK_HOLE:
                if (offset >= i_size) {
                        ret = -ENXIO;
                        goto out;
                }
                offset = i_size;
                break;
        }

        ret = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);

out:
        inode_unlock(inode);
        return ret;
}

static inline void ceph_zero_partial_page(
        struct inode *inode, loff_t offset, unsigned size)
{
        struct page *page;
        pgoff_t index = offset >> PAGE_SHIFT;

        page = find_lock_page(inode->i_mapping, index);
        if (page) {
                wait_on_page_writeback(page);
                zero_user(page, offset & (PAGE_SIZE - 1), size);
                unlock_page(page);
                put_page(page);
        }
}

static void ceph_zero_pagecache_range(struct inode *inode, loff_t offset,
                                      loff_t length)
{
        loff_t nearly = round_up(offset, PAGE_SIZE);
        if (offset < nearly) {
                loff_t size = nearly - offset;
                if (length < size)
                        size = length;
                ceph_zero_partial_page(inode, offset, size);
                offset += size;
                length -= size;
        }
        if (length >= PAGE_SIZE) {
                loff_t size = round_down(length, PAGE_SIZE);
                truncate_pagecache_range(inode, offset, offset + size - 1);
                offset += size;
                length -= size;
        }
        if (length)
                ceph_zero_partial_page(inode, offset, length);
}

static int ceph_zero_partial_object(struct inode *inode,
                                    loff_t offset, loff_t *length)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_osd_request *req;
        int ret = 0;
        loff_t zero = 0;
        int op;

        if (!length) {
                op = offset ? CEPH_OSD_OP_DELETE : CEPH_OSD_OP_TRUNCATE;
                length = &zero;
        } else {
                op = CEPH_OSD_OP_ZERO;
        }

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                        ceph_vino(inode),
                                        offset, length,
                                        0, 1, op,
                                        CEPH_OSD_FLAG_WRITE,
                                        NULL, 0, 0, false);
        if (IS_ERR(req)) {
                ret = PTR_ERR(req);
                goto out;
        }

        req->r_mtime = inode->i_mtime;
        ret = ceph_osdc_start_request(&fsc->client->osdc, req, false);
        if (!ret) {
                ret = ceph_osdc_wait_request(&fsc->client->osdc, req);
                if (ret == -ENOENT)
                        ret = 0;
        }
        ceph_osdc_put_request(req);

out:
        return ret;
}

static int ceph_zero_objects(struct inode *inode, loff_t offset, loff_t length)
{
        int ret = 0;
        struct ceph_inode_info *ci = ceph_inode(inode);
        s32 stripe_unit = ci->i_layout.stripe_unit;
        s32 stripe_count = ci->i_layout.stripe_count;
        s32 object_size = ci->i_layout.object_size;
        u64 object_set_size = object_size * stripe_count;
        u64 nearly, t;

        /* round offset up to next period boundary */
        nearly = offset + object_set_size - 1;
        t = nearly;
        nearly -= do_div(t, object_set_size);

        while (length && offset < nearly) {
                loff_t size = length;
                ret = ceph_zero_partial_object(inode, offset, &size);
                if (ret < 0)
                        return ret;
                offset += size;
                length -= size;
        }
        while (length >= object_set_size) {
                int i;
                loff_t pos = offset;
                for (i = 0; i < stripe_count; ++i) {
                        ret = ceph_zero_partial_object(inode, pos, NULL);
                        if (ret < 0)
                                return ret;
                        pos += stripe_unit;
                }
                offset += object_set_size;
                length -= object_set_size;
        }
        while (length) {
                loff_t size = length;
                ret = ceph_zero_partial_object(inode, offset, &size);
                if (ret < 0)
                        return ret;
                offset += size;
                length -= size;
        }
        return ret;
}

static long ceph_fallocate(struct file *file, int mode,
                                loff_t offset, loff_t length)
{
        struct ceph_file_info *fi = file->private_data;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_osd_client *osdc =
                &ceph_inode_to_client(inode)->client->osdc;
        struct ceph_cap_flush *prealloc_cf;
        int want, got = 0;
        int dirty;
        int ret = 0;
        loff_t endoff = 0;
        loff_t size;

        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
                return -EOPNOTSUPP;

        if (!S_ISREG(inode->i_mode))
                return -EOPNOTSUPP;

        prealloc_cf = ceph_alloc_cap_flush();
        if (!prealloc_cf)
                return -ENOMEM;

        inode_lock(inode);

        if (ceph_snap(inode) != CEPH_NOSNAP) {
                ret = -EROFS;
                goto unlock;
        }

        if (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) &&
            !(mode & FALLOC_FL_PUNCH_HOLE)) {
                ret = -ENOSPC;
                goto unlock;
        }

        if (ci->i_inline_version != CEPH_INLINE_NONE) {
                ret = ceph_uninline_data(file, NULL);
                if (ret < 0)
                        goto unlock;
        }

        size = i_size_read(inode);
        if (!(mode & FALLOC_FL_KEEP_SIZE))
                endoff = offset + length;

        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_BUFFER;

        ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, endoff, &got, NULL);
        if (ret < 0)
                goto unlock;

        if (mode & FALLOC_FL_PUNCH_HOLE) {
                if (offset < size)
                        ceph_zero_pagecache_range(inode, offset, length);
                ret = ceph_zero_objects(inode, offset, length);
        } else if (endoff > size) {
                truncate_pagecache_range(inode, size, -1);
                if (ceph_inode_set_size(inode, endoff))
                        ceph_check_caps(ceph_inode(inode),
                                CHECK_CAPS_AUTHONLY, NULL);
        }

        if (!ret) {
                spin_lock(&ci->i_ceph_lock);
                ci->i_inline_version = CEPH_INLINE_NONE;
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
                                               &prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);
        }

        ceph_put_cap_refs(ci, got);
unlock:
        inode_unlock(inode);
        ceph_free_cap_flush(prealloc_cf);
        return ret;
}

const struct file_operations ceph_file_fops = {
        .open = ceph_open,
        .release = ceph_release,
        .llseek = ceph_llseek,
        .read_iter = ceph_read_iter,
        .write_iter = ceph_write_iter,
        .mmap = ceph_mmap,
        .fsync = ceph_fsync,
        .lock = ceph_lock,
        .flock = ceph_flock,
        .splice_read = generic_file_splice_read,
        .splice_write = iter_file_splice_write,
        .unlocked_ioctl = ceph_ioctl,
        .compat_ioctl   = ceph_ioctl,
        .fallocate      = ceph_fallocate,
};