ceph: quota: support for ceph.quota.max_files

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

// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/spinlock.h>
#include <linux/fs_struct.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/xattr.h>

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

/*
 * Directory operations: readdir, lookup, create, link, unlink,
 * rename, etc.
 */

/*
 * Ceph MDS operations are specified in terms of a base ino and
 * relative path.  Thus, the client can specify an operation on a
 * specific inode (e.g., a getattr due to fstat(2)), or as a path
 * relative to, say, the root directory.
 *
 * Normally, we limit ourselves to strict inode ops (no path component)
 * or dentry operations (a single path component relative to an ino).  The
 * exception to this is open_root_dentry(), which will open the mount
 * point by name.
 */

const struct dentry_operations ceph_dentry_ops;

/*
 * Initialize ceph dentry state.
 */
static int ceph_d_init(struct dentry *dentry)
{
        struct ceph_dentry_info *di;

        di = kmem_cache_zalloc(ceph_dentry_cachep, GFP_KERNEL);
        if (!di)
                return -ENOMEM;          /* oh well */

        di->dentry = dentry;
        di->lease_session = NULL;
        di->time = jiffies;
        dentry->d_fsdata = di;
        ceph_dentry_lru_add(dentry);
        return 0;
}

/*
 * for f_pos for readdir:
 * - hash order:
 *      (0xff << 52) | ((24 bits hash) << 28) |
 *      (the nth entry has hash collision);
 * - frag+name order;
 *      ((frag value) << 28) | (the nth entry in frag);
 */
#define OFFSET_BITS     28
#define OFFSET_MASK     ((1 << OFFSET_BITS) - 1)
#define HASH_ORDER      (0xffull << (OFFSET_BITS + 24))
loff_t ceph_make_fpos(unsigned high, unsigned off, bool hash_order)
{
        loff_t fpos = ((loff_t)high << 28) | (loff_t)off;
        if (hash_order)
                fpos |= HASH_ORDER;
        return fpos;
}

static bool is_hash_order(loff_t p)
{
        return (p & HASH_ORDER) == HASH_ORDER;
}

static unsigned fpos_frag(loff_t p)
{
        return p >> OFFSET_BITS;
}

static unsigned fpos_hash(loff_t p)
{
        return ceph_frag_value(fpos_frag(p));
}

static unsigned fpos_off(loff_t p)
{
        return p & OFFSET_MASK;
}

static int fpos_cmp(loff_t l, loff_t r)
{
        int v = ceph_frag_compare(fpos_frag(l), fpos_frag(r));
        if (v)
                return v;
        return (int)(fpos_off(l) - fpos_off(r));
}

/*
 * make note of the last dentry we read, so we can
 * continue at the same lexicographical point,
 * regardless of what dir changes take place on the
 * server.
 */
static int note_last_dentry(struct ceph_file_info *fi, const char *name,
                            int len, unsigned next_offset)
{
        char *buf = kmalloc(len+1, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        kfree(fi->last_name);
        fi->last_name = buf;
        memcpy(fi->last_name, name, len);
        fi->last_name[len] = 0;
        fi->next_offset = next_offset;
        dout("note_last_dentry '%s'\n", fi->last_name);
        return 0;
}


static struct dentry *
__dcache_find_get_entry(struct dentry *parent, u64 idx,
                        struct ceph_readdir_cache_control *cache_ctl)
{
        struct inode *dir = d_inode(parent);
        struct dentry *dentry;
        unsigned idx_mask = (PAGE_SIZE / sizeof(struct dentry *)) - 1;
        loff_t ptr_pos = idx * sizeof(struct dentry *);
        pgoff_t ptr_pgoff = ptr_pos >> PAGE_SHIFT;

        if (ptr_pos >= i_size_read(dir))
                return NULL;

        if (!cache_ctl->page || ptr_pgoff != page_index(cache_ctl->page)) {
                ceph_readdir_cache_release(cache_ctl);
                cache_ctl->page = find_lock_page(&dir->i_data, ptr_pgoff);
                if (!cache_ctl->page) {
                        dout(" page %lu not found\n", ptr_pgoff);
                        return ERR_PTR(-EAGAIN);
                }
                /* reading/filling the cache are serialized by
                   i_mutex, no need to use page lock */
                unlock_page(cache_ctl->page);
                cache_ctl->dentries = kmap(cache_ctl->page);
        }

        cache_ctl->index = idx & idx_mask;

        rcu_read_lock();
        spin_lock(&parent->d_lock);
        /* check i_size again here, because empty directory can be
         * marked as complete while not holding the i_mutex. */
        if (ceph_dir_is_complete_ordered(dir) && ptr_pos < i_size_read(dir))
                dentry = cache_ctl->dentries[cache_ctl->index];
        else
                dentry = NULL;
        spin_unlock(&parent->d_lock);
        if (dentry && !lockref_get_not_dead(&dentry->d_lockref))
                dentry = NULL;
        rcu_read_unlock();
        return dentry ? : ERR_PTR(-EAGAIN);
}

/*
 * When possible, we try to satisfy a readdir by peeking at the
 * dcache.  We make this work by carefully ordering dentries on
 * d_child when we initially get results back from the MDS, and
 * falling back to a "normal" sync readdir if any dentries in the dir
 * are dropped.
 *
 * Complete dir indicates that we have all dentries in the dir.  It is
 * defined IFF we hold CEPH_CAP_FILE_SHARED (which will be revoked by
 * the MDS if/when the directory is modified).
 */
static int __dcache_readdir(struct file *file,  struct dir_context *ctx,
                            int shared_gen)
{
        struct ceph_file_info *fi = file->private_data;
        struct dentry *parent = file->f_path.dentry;
        struct inode *dir = d_inode(parent);
        struct dentry *dentry, *last = NULL;
        struct ceph_dentry_info *di;
        struct ceph_readdir_cache_control cache_ctl = {};
        u64 idx = 0;
        int err = 0;

        dout("__dcache_readdir %p v%u at %llx\n", dir, (unsigned)shared_gen, ctx->pos);

        /* search start position */
        if (ctx->pos > 2) {
                u64 count = div_u64(i_size_read(dir), sizeof(struct dentry *));
                while (count > 0) {
                        u64 step = count >> 1;
                        dentry = __dcache_find_get_entry(parent, idx + step,
                                                         &cache_ctl);
                        if (!dentry) {
                                /* use linar search */
                                idx = 0;
                                break;
                        }
                        if (IS_ERR(dentry)) {
                                err = PTR_ERR(dentry);
                                goto out;
                        }
                        di = ceph_dentry(dentry);
                        spin_lock(&dentry->d_lock);
                        if (fpos_cmp(di->offset, ctx->pos) < 0) {
                                idx += step + 1;
                                count -= step + 1;
                        } else {
                                count = step;
                        }
                        spin_unlock(&dentry->d_lock);
                        dput(dentry);
                }

                dout("__dcache_readdir %p cache idx %llu\n", dir, idx);
        }


        for (;;) {
                bool emit_dentry = false;
                dentry = __dcache_find_get_entry(parent, idx++, &cache_ctl);
                if (!dentry) {
                        fi->flags |= CEPH_F_ATEND;
                        err = 0;
                        break;
                }
                if (IS_ERR(dentry)) {
                        err = PTR_ERR(dentry);
                        goto out;
                }

                spin_lock(&dentry->d_lock);
                di = ceph_dentry(dentry);
                if (d_unhashed(dentry) ||
                    d_really_is_negative(dentry) ||
                    di->lease_shared_gen != shared_gen) {
                        spin_unlock(&dentry->d_lock);
                        dput(dentry);
                        err = -EAGAIN;
                        goto out;
                }
                if (fpos_cmp(ctx->pos, di->offset) <= 0) {
                        emit_dentry = true;
                }
                spin_unlock(&dentry->d_lock);

                if (emit_dentry) {
                        dout(" %llx dentry %p %pd %p\n", di->offset,
                             dentry, dentry, d_inode(dentry));
                        ctx->pos = di->offset;
                        if (!dir_emit(ctx, dentry->d_name.name,
                                      dentry->d_name.len,
                                      ceph_translate_ino(dentry->d_sb,
                                                         d_inode(dentry)->i_ino),
                                      d_inode(dentry)->i_mode >> 12)) {
                                dput(dentry);
                                err = 0;
                                break;
                        }
                        ctx->pos++;

                        if (last)
                                dput(last);
                        last = dentry;
                } else {
                        dput(dentry);
                }
        }
out:
        ceph_readdir_cache_release(&cache_ctl);
        if (last) {
                int ret;
                di = ceph_dentry(last);
                ret = note_last_dentry(fi, last->d_name.name, last->d_name.len,
                                       fpos_off(di->offset) + 1);
                if (ret < 0)
                        err = ret;
                dput(last);
                /* last_name no longer match cache index */
                if (fi->readdir_cache_idx >= 0) {
                        fi->readdir_cache_idx = -1;
                        fi->dir_release_count = 0;
                }
        }
        return err;
}

static bool need_send_readdir(struct ceph_file_info *fi, loff_t pos)
{
        if (!fi->last_readdir)
                return true;
        if (is_hash_order(pos))
                return !ceph_frag_contains_value(fi->frag, fpos_hash(pos));
        else
                return fi->frag != fpos_frag(pos);
}

static int ceph_readdir(struct file *file, struct dir_context *ctx)
{
        struct ceph_file_info *fi = file->private_data;
        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_mds_client *mdsc = fsc->mdsc;
        int i;
        int err;
        unsigned frag = -1;
        struct ceph_mds_reply_info_parsed *rinfo;

        dout("readdir %p file %p pos %llx\n", inode, file, ctx->pos);
        if (fi->flags & CEPH_F_ATEND)
                return 0;

        /* always start with . and .. */
        if (ctx->pos == 0) {
                dout("readdir off 0 -> '.'\n");
                if (!dir_emit(ctx, ".", 1, 
                            ceph_translate_ino(inode->i_sb, inode->i_ino),
                            inode->i_mode >> 12))
                        return 0;
                ctx->pos = 1;
        }
        if (ctx->pos == 1) {
                ino_t ino = parent_ino(file->f_path.dentry);
                dout("readdir off 1 -> '..'\n");
                if (!dir_emit(ctx, "..", 2,
                            ceph_translate_ino(inode->i_sb, ino),
                            inode->i_mode >> 12))
                        return 0;
                ctx->pos = 2;
        }

        /* can we use the dcache? */
        spin_lock(&ci->i_ceph_lock);
        if (ceph_test_mount_opt(fsc, DCACHE) &&
            !ceph_test_mount_opt(fsc, NOASYNCREADDIR) &&
            ceph_snap(inode) != CEPH_SNAPDIR &&
            __ceph_dir_is_complete_ordered(ci) &&
            __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1)) {
                int shared_gen = atomic_read(&ci->i_shared_gen);
                spin_unlock(&ci->i_ceph_lock);
                err = __dcache_readdir(file, ctx, shared_gen);
                if (err != -EAGAIN)
                        return err;
        } else {
                spin_unlock(&ci->i_ceph_lock);
        }

        /* proceed with a normal readdir */
more:
        /* do we have the correct frag content buffered? */
        if (need_send_readdir(fi, ctx->pos)) {
                struct ceph_mds_request *req;
                int op = ceph_snap(inode) == CEPH_SNAPDIR ?
                        CEPH_MDS_OP_LSSNAP : CEPH_MDS_OP_READDIR;

                /* discard old result, if any */
                if (fi->last_readdir) {
                        ceph_mdsc_put_request(fi->last_readdir);
                        fi->last_readdir = NULL;
                }

                if (is_hash_order(ctx->pos)) {
                        /* fragtree isn't always accurate. choose frag
                         * based on previous reply when possible. */
                        if (frag == (unsigned)-1)
                                frag = ceph_choose_frag(ci, fpos_hash(ctx->pos),
                                                        NULL, NULL);
                } else {
                        frag = fpos_frag(ctx->pos);
                }

                dout("readdir fetching %llx.%llx frag %x offset '%s'\n",
                     ceph_vinop(inode), frag, fi->last_name);
                req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
                if (IS_ERR(req))
                        return PTR_ERR(req);
                err = ceph_alloc_readdir_reply_buffer(req, inode);
                if (err) {
                        ceph_mdsc_put_request(req);
                        return err;
                }
                /* hints to request -> mds selection code */
                req->r_direct_mode = USE_AUTH_MDS;
                if (op == CEPH_MDS_OP_READDIR) {
                        req->r_direct_hash = ceph_frag_value(frag);
                        __set_bit(CEPH_MDS_R_DIRECT_IS_HASH, &req->r_req_flags);
                }
                if (fi->last_name) {
                        req->r_path2 = kstrdup(fi->last_name, GFP_KERNEL);
                        if (!req->r_path2) {
                                ceph_mdsc_put_request(req);
                                return -ENOMEM;
                        }
                } else if (is_hash_order(ctx->pos)) {
                        req->r_args.readdir.offset_hash =
                                cpu_to_le32(fpos_hash(ctx->pos));
                }

                req->r_dir_release_cnt = fi->dir_release_count;
                req->r_dir_ordered_cnt = fi->dir_ordered_count;
                req->r_readdir_cache_idx = fi->readdir_cache_idx;
                req->r_readdir_offset = fi->next_offset;
                req->r_args.readdir.frag = cpu_to_le32(frag);
                req->r_args.readdir.flags =
                                cpu_to_le16(CEPH_READDIR_REPLY_BITFLAGS);

                req->r_inode = inode;
                ihold(inode);
                req->r_dentry = dget(file->f_path.dentry);
                err = ceph_mdsc_do_request(mdsc, NULL, req);
                if (err < 0) {
                        ceph_mdsc_put_request(req);
                        return err;
                }
                dout("readdir got and parsed readdir result=%d on "
                     "frag %x, end=%d, complete=%d, hash_order=%d\n",
                     err, frag,
                     (int)req->r_reply_info.dir_end,
                     (int)req->r_reply_info.dir_complete,
                     (int)req->r_reply_info.hash_order);

                rinfo = &req->r_reply_info;
                if (le32_to_cpu(rinfo->dir_dir->frag) != frag) {
                        frag = le32_to_cpu(rinfo->dir_dir->frag);
                        if (!rinfo->hash_order) {
                                fi->next_offset = req->r_readdir_offset;
                                /* adjust ctx->pos to beginning of frag */
                                ctx->pos = ceph_make_fpos(frag,
                                                          fi->next_offset,
                                                          false);
                        }
                }

                fi->frag = frag;
                fi->last_readdir = req;

                if (test_bit(CEPH_MDS_R_DID_PREPOPULATE, &req->r_req_flags)) {
                        fi->readdir_cache_idx = req->r_readdir_cache_idx;
                        if (fi->readdir_cache_idx < 0) {
                                /* preclude from marking dir ordered */
                                fi->dir_ordered_count = 0;
                        } else if (ceph_frag_is_leftmost(frag) &&
                                   fi->next_offset == 2) {
                                /* note dir version at start of readdir so
                                 * we can tell if any dentries get dropped */
                                fi->dir_release_count = req->r_dir_release_cnt;
                                fi->dir_ordered_count = req->r_dir_ordered_cnt;
                        }
                } else {
                        dout("readdir !did_prepopulate");
                        /* disable readdir cache */
                        fi->readdir_cache_idx = -1;
                        /* preclude from marking dir complete */
                        fi->dir_release_count = 0;
                }

                /* note next offset and last dentry name */
                if (rinfo->dir_nr > 0) {
                        struct ceph_mds_reply_dir_entry *rde =
                                        rinfo->dir_entries + (rinfo->dir_nr-1);
                        unsigned next_offset = req->r_reply_info.dir_end ?
                                        2 : (fpos_off(rde->offset) + 1);
                        err = note_last_dentry(fi, rde->name, rde->name_len,
                                               next_offset);
                        if (err)
                                return err;
                } else if (req->r_reply_info.dir_end) {
                        fi->next_offset = 2;
                        /* keep last name */
                }
        }

        rinfo = &fi->last_readdir->r_reply_info;
        dout("readdir frag %x num %d pos %llx chunk first %llx\n",
             fi->frag, rinfo->dir_nr, ctx->pos,
             rinfo->dir_nr ? rinfo->dir_entries[0].offset : 0LL);

        i = 0;
        /* search start position */
        if (rinfo->dir_nr > 0) {
                int step, nr = rinfo->dir_nr;
                while (nr > 0) {
                        step = nr >> 1;
                        if (rinfo->dir_entries[i + step].offset < ctx->pos) {
                                i +=  step + 1;
                                nr -= step + 1;
                        } else {
                                nr = step;
                        }
                }
        }
        for (; i < rinfo->dir_nr; i++) {
                struct ceph_mds_reply_dir_entry *rde = rinfo->dir_entries + i;
                struct ceph_vino vino;
                ino_t ino;
                u32 ftype;

                BUG_ON(rde->offset < ctx->pos);

                ctx->pos = rde->offset;
                dout("readdir (%d/%d) -> %llx '%.*s' %p\n",
                     i, rinfo->dir_nr, ctx->pos,
                     rde->name_len, rde->name, &rde->inode.in);

                BUG_ON(!rde->inode.in);
                ftype = le32_to_cpu(rde->inode.in->mode) >> 12;
                vino.ino = le64_to_cpu(rde->inode.in->ino);
                vino.snap = le64_to_cpu(rde->inode.in->snapid);
                ino = ceph_vino_to_ino(vino);

                if (!dir_emit(ctx, rde->name, rde->name_len,
                              ceph_translate_ino(inode->i_sb, ino), ftype)) {
                        dout("filldir stopping us...\n");
                        return 0;
                }
                ctx->pos++;
        }

        ceph_mdsc_put_request(fi->last_readdir);
        fi->last_readdir = NULL;

        if (fi->next_offset > 2) {
                frag = fi->frag;
                goto more;
        }

        /* more frags? */
        if (!ceph_frag_is_rightmost(fi->frag)) {
                frag = ceph_frag_next(fi->frag);
                if (is_hash_order(ctx->pos)) {
                        loff_t new_pos = ceph_make_fpos(ceph_frag_value(frag),
                                                        fi->next_offset, true);
                        if (new_pos > ctx->pos)
                                ctx->pos = new_pos;
                        /* keep last_name */
                } else {
                        ctx->pos = ceph_make_fpos(frag, fi->next_offset, false);
                        kfree(fi->last_name);
                        fi->last_name = NULL;
                }
                dout("readdir next frag is %x\n", frag);
                goto more;
        }
        fi->flags |= CEPH_F_ATEND;

        /*
         * if dir_release_count still matches the dir, no dentries
         * were released during the whole readdir, and we should have
         * the complete dir contents in our cache.
         */
        if (atomic64_read(&ci->i_release_count) == fi->dir_release_count) {
                spin_lock(&ci->i_ceph_lock);
                if (fi->dir_ordered_count == atomic64_read(&ci->i_ordered_count)) {
                        dout(" marking %p complete and ordered\n", inode);
                        /* use i_size to track number of entries in
                         * readdir cache */
                        BUG_ON(fi->readdir_cache_idx < 0);
                        i_size_write(inode, fi->readdir_cache_idx *
                                     sizeof(struct dentry*));
                } else {
                        dout(" marking %p complete\n", inode);
                }
                __ceph_dir_set_complete(ci, fi->dir_release_count,
                                        fi->dir_ordered_count);
                spin_unlock(&ci->i_ceph_lock);
        }

        dout("readdir %p file %p done.\n", inode, file);
        return 0;
}

static void reset_readdir(struct ceph_file_info *fi)
{
        if (fi->last_readdir) {
                ceph_mdsc_put_request(fi->last_readdir);
                fi->last_readdir = NULL;
        }
        kfree(fi->last_name);
        fi->last_name = NULL;
        fi->dir_release_count = 0;
        fi->readdir_cache_idx = -1;
        fi->next_offset = 2;  /* compensate for . and .. */
        fi->flags &= ~CEPH_F_ATEND;
}

/*
 * discard buffered readdir content on seekdir(0), or seek to new frag,
 * or seek prior to current chunk
 */
static bool need_reset_readdir(struct ceph_file_info *fi, loff_t new_pos)
{
        struct ceph_mds_reply_info_parsed *rinfo;
        loff_t chunk_offset;
        if (new_pos == 0)
                return true;
        if (is_hash_order(new_pos)) {
                /* no need to reset last_name for a forward seek when
                 * dentries are sotred in hash order */
        } else if (fi->frag != fpos_frag(new_pos)) {
                return true;
        }
        rinfo = fi->last_readdir ? &fi->last_readdir->r_reply_info : NULL;
        if (!rinfo || !rinfo->dir_nr)
                return true;
        chunk_offset = rinfo->dir_entries[0].offset;
        return new_pos < chunk_offset ||
               is_hash_order(new_pos) != is_hash_order(chunk_offset);
}

static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
{
        struct ceph_file_info *fi = file->private_data;
        struct inode *inode = file->f_mapping->host;
        loff_t retval;

        inode_lock(inode);
        retval = -EINVAL;
        switch (whence) {
        case SEEK_CUR:
                offset += file->f_pos;
        case SEEK_SET:
                break;
        case SEEK_END:
                retval = -EOPNOTSUPP;
        default:
                goto out;
        }

        if (offset >= 0) {
                if (need_reset_readdir(fi, offset)) {
                        dout("dir_llseek dropping %p content\n", file);
                        reset_readdir(fi);
                } else if (is_hash_order(offset) && offset > file->f_pos) {
                        /* for hash offset, we don't know if a forward seek
                         * is within same frag */
                        fi->dir_release_count = 0;
                        fi->readdir_cache_idx = -1;
                }

                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                        fi->flags &= ~CEPH_F_ATEND;
                }
                retval = offset;
        }
out:
        inode_unlock(inode);
        return retval;
}

/*
 * Handle lookups for the hidden .snap directory.
 */
int ceph_handle_snapdir(struct ceph_mds_request *req,
                        struct dentry *dentry, int err)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
        struct inode *parent = d_inode(dentry->d_parent); /* we hold i_mutex */

        /* .snap dir? */
        if (err == -ENOENT &&
            ceph_snap(parent) == CEPH_NOSNAP &&
            strcmp(dentry->d_name.name,
                   fsc->mount_options->snapdir_name) == 0) {
                struct inode *inode = ceph_get_snapdir(parent);
                dout("ENOENT on snapdir %p '%pd', linking to snapdir %p\n",
                     dentry, dentry, inode);
                BUG_ON(!d_unhashed(dentry));
                d_add(dentry, inode);
                err = 0;
        }
        return err;
}

/*
 * Figure out final result of a lookup/open request.
 *
 * Mainly, make sure we return the final req->r_dentry (if it already
 * existed) in place of the original VFS-provided dentry when they
 * differ.
 *
 * Gracefully handle the case where the MDS replies with -ENOENT and
 * no trace (which it may do, at its discretion, e.g., if it doesn't
 * care to issue a lease on the negative dentry).
 */
struct dentry *ceph_finish_lookup(struct ceph_mds_request *req,
                                  struct dentry *dentry, int err)
{
        if (err == -ENOENT) {
                /* no trace? */
                err = 0;
                if (!req->r_reply_info.head->is_dentry) {
                        dout("ENOENT and no trace, dentry %p inode %p\n",
                             dentry, d_inode(dentry));
                        if (d_really_is_positive(dentry)) {
                                d_drop(dentry);
                                err = -ENOENT;
                        } else {
                                d_add(dentry, NULL);
                        }
                }
        }
        if (err)
                dentry = ERR_PTR(err);
        else if (dentry != req->r_dentry)
                dentry = dget(req->r_dentry);   /* we got spliced */
        else
                dentry = NULL;
        return dentry;
}

static bool is_root_ceph_dentry(struct inode *inode, struct dentry *dentry)
{
        return ceph_ino(inode) == CEPH_INO_ROOT &&
                strncmp(dentry->d_name.name, ".ceph", 5) == 0;
}

/*
 * Look up a single dir entry.  If there is a lookup intent, inform
 * the MDS so that it gets our 'caps wanted' value in a single op.
 */
static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
                                  unsigned int flags)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int op;
        int mask;
        int err;

        dout("lookup %p dentry %p '%pd'\n",
             dir, dentry, dentry);

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

        /* can we conclude ENOENT locally? */
        if (d_really_is_negative(dentry)) {
                struct ceph_inode_info *ci = ceph_inode(dir);
                struct ceph_dentry_info *di = ceph_dentry(dentry);

                spin_lock(&ci->i_ceph_lock);
                dout(" dir %p flags are %d\n", dir, ci->i_ceph_flags);
                if (strncmp(dentry->d_name.name,
                            fsc->mount_options->snapdir_name,
                            dentry->d_name.len) &&
                    !is_root_ceph_dentry(dir, dentry) &&
                    ceph_test_mount_opt(fsc, DCACHE) &&
                    __ceph_dir_is_complete(ci) &&
                    (__ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1))) {
                        spin_unlock(&ci->i_ceph_lock);
                        dout(" dir %p complete, -ENOENT\n", dir);
                        d_add(dentry, NULL);
                        di->lease_shared_gen = atomic_read(&ci->i_shared_gen);
                        return NULL;
                }
                spin_unlock(&ci->i_ceph_lock);
        }

        op = ceph_snap(dir) == CEPH_SNAPDIR ?
                CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_LOOKUP;
        req = ceph_mdsc_create_request(mdsc, op, USE_ANY_MDS);
        if (IS_ERR(req))
                return ERR_CAST(req);
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;

        mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
        if (ceph_security_xattr_wanted(dir))
                mask |= CEPH_CAP_XATTR_SHARED;
        req->r_args.getattr.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, NULL, req);
        err = ceph_handle_snapdir(req, dentry, err);
        dentry = ceph_finish_lookup(req, dentry, err);
        ceph_mdsc_put_request(req);  /* will dput(dentry) */
        dout("lookup result=%p\n", dentry);
        return dentry;
}

/*
 * If we do a create but get no trace back from the MDS, follow up with
 * a lookup (the VFS expects us to link up the provided dentry).
 */
int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry)
{
        struct dentry *result = ceph_lookup(dir, dentry, 0);

        if (result && !IS_ERR(result)) {
                /*
                 * We created the item, then did a lookup, and found
                 * it was already linked to another inode we already
                 * had in our cache (and thus got spliced). To not
                 * confuse VFS (especially when inode is a directory),
                 * we don't link our dentry to that inode, return an
                 * error instead.
                 *
                 * This event should be rare and it happens only when
                 * we talk to old MDS. Recent MDS does not send traceless
                 * reply for request that creates new inode.
                 */
                d_drop(result);
                return -ESTALE;
        }
        return PTR_ERR(result);
}

static int ceph_mknod(struct inode *dir, struct dentry *dentry,
                      umode_t mode, dev_t rdev)
{
        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 ceph_acls_info acls = {};
        int err;

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

        if (ceph_quota_is_max_files_exceeded(dir))
                return -EDQUOT;

        err = ceph_pre_init_acls(dir, &mode, &acls);
        if (err < 0)
                return err;

        dout("mknod in dir %p dentry %p mode 0%ho rdev %d\n",
             dir, dentry, mode, rdev);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_MKNOD, USE_AUTH_MDS);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_args.mknod.mode = cpu_to_le32(mode);
        req->r_args.mknod.rdev = cpu_to_le32(rdev);
        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;
        }
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (!err && !req->r_reply_info.head->is_dentry)
                err = ceph_handle_notrace_create(dir, dentry);
        ceph_mdsc_put_request(req);
out:
        if (!err)
                ceph_init_inode_acls(d_inode(dentry), &acls);
        else
                d_drop(dentry);
        ceph_release_acls_info(&acls);
        return err;
}

static int ceph_create(struct inode *dir, struct dentry *dentry, umode_t mode,
                       bool excl)
{
        return ceph_mknod(dir, dentry, mode, 0);
}

static int ceph_symlink(struct inode *dir, struct dentry *dentry,
                            const char *dest)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int err;

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

        if (ceph_quota_is_max_files_exceeded(dir))
                return -EDQUOT;

        dout("symlink in dir %p dentry %p to '%s'\n", dir, dentry, dest);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_SYMLINK, USE_AUTH_MDS);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }
        req->r_path2 = kstrdup(dest, GFP_KERNEL);
        if (!req->r_path2) {
                err = -ENOMEM;
                ceph_mdsc_put_request(req);
                goto out;
        }
        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (!err && !req->r_reply_info.head->is_dentry)
                err = ceph_handle_notrace_create(dir, dentry);
        ceph_mdsc_put_request(req);
out:
        if (err)
                d_drop(dentry);
        return err;
}

static int ceph_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        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 ceph_acls_info acls = {};
        int err = -EROFS;
        int op;

        if (ceph_snap(dir) == CEPH_SNAPDIR) {
                /* mkdir .snap/foo is a MKSNAP */
                op = CEPH_MDS_OP_MKSNAP;
                dout("mksnap dir %p snap '%pd' dn %p\n", dir,
                     dentry, dentry);
        } else if (ceph_snap(dir) == CEPH_NOSNAP) {
                dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode);
                op = CEPH_MDS_OP_MKDIR;
        } else {
                goto out;
        }

        if (ceph_quota_is_max_files_exceeded(dir)) {
                err = -EDQUOT;
                goto out;
        }

        mode |= S_IFDIR;
        err = ceph_pre_init_acls(dir, &mode, &acls);
        if (err < 0)
                goto out;

        req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }

        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_args.mkdir.mode = cpu_to_le32(mode);
        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;
        }
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (!err &&
            !req->r_reply_info.head->is_target &&
            !req->r_reply_info.head->is_dentry)
                err = ceph_handle_notrace_create(dir, dentry);
        ceph_mdsc_put_request(req);
out:
        if (!err)
                ceph_init_inode_acls(d_inode(dentry), &acls);
        else
                d_drop(dentry);
        ceph_release_acls_info(&acls);
        return err;
}

static int ceph_link(struct dentry *old_dentry, struct inode *dir,
                     struct dentry *dentry)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int err;

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

        dout("link in dir %p old_dentry %p dentry %p\n", dir,
             old_dentry, dentry);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LINK, USE_AUTH_MDS);
        if (IS_ERR(req)) {
                d_drop(dentry);
                return PTR_ERR(req);
        }
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        req->r_old_dentry = dget(old_dentry);
        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        /* release LINK_SHARED on source inode (mds will lock it) */
        req->r_old_inode_drop = CEPH_CAP_LINK_SHARED;
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (err) {
                d_drop(dentry);
        } else if (!req->r_reply_info.head->is_dentry) {
                ihold(d_inode(old_dentry));
                d_instantiate(dentry, d_inode(old_dentry));
        }
        ceph_mdsc_put_request(req);
        return err;
}

/*
 * For a soon-to-be unlinked file, drop the AUTH_RDCACHE caps.  If it
 * looks like the link count will hit 0, drop any other caps (other
 * than PIN) we don't specifically want (due to the file still being
 * open).
 */
static int drop_caps_for_unlink(struct inode *inode)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        int drop = CEPH_CAP_LINK_SHARED | CEPH_CAP_LINK_EXCL;

        spin_lock(&ci->i_ceph_lock);
        if (inode->i_nlink == 1) {
                drop |= ~(__ceph_caps_wanted(ci) | CEPH_CAP_PIN);
                ci->i_ceph_flags |= CEPH_I_NODELAY;
        }
        spin_unlock(&ci->i_ceph_lock);
        return drop;
}

/*
 * rmdir and unlink are differ only by the metadata op code
 */
static int ceph_unlink(struct inode *dir, struct dentry *dentry)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct inode *inode = d_inode(dentry);
        struct ceph_mds_request *req;
        int err = -EROFS;
        int op;

        if (ceph_snap(dir) == CEPH_SNAPDIR) {
                /* rmdir .snap/foo is RMSNAP */
                dout("rmsnap dir %p '%pd' dn %p\n", dir, dentry, dentry);
                op = CEPH_MDS_OP_RMSNAP;
        } else if (ceph_snap(dir) == CEPH_NOSNAP) {
                dout("unlink/rmdir dir %p dn %p inode %p\n",
                     dir, dentry, inode);
                op = d_is_dir(dentry) ?
                        CEPH_MDS_OP_RMDIR : CEPH_MDS_OP_UNLINK;
        } else
                goto out;
        req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }
        req->r_dentry = dget(dentry);
        req->r_num_caps = 2;
        req->r_parent = dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        req->r_inode_drop = drop_caps_for_unlink(inode);
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (!err && !req->r_reply_info.head->is_dentry)
                d_delete(dentry);
        ceph_mdsc_put_request(req);
out:
        return err;
}

static int ceph_rename(struct inode *old_dir, struct dentry *old_dentry,
                       struct inode *new_dir, struct dentry *new_dentry,
                       unsigned int flags)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(old_dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int op = CEPH_MDS_OP_RENAME;
        int err;

        if (flags)
                return -EINVAL;

        if (ceph_snap(old_dir) != ceph_snap(new_dir))
                return -EXDEV;
        if (ceph_snap(old_dir) != CEPH_NOSNAP) {
                if (old_dir == new_dir && ceph_snap(old_dir) == CEPH_SNAPDIR)
                        op = CEPH_MDS_OP_RENAMESNAP;
                else
                        return -EROFS;
        }
        dout("rename dir %p dentry %p to dir %p dentry %p\n",
             old_dir, old_dentry, new_dir, new_dentry);
        req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
        if (IS_ERR(req))
                return PTR_ERR(req);
        ihold(old_dir);
        req->r_dentry = dget(new_dentry);
        req->r_num_caps = 2;
        req->r_old_dentry = dget(old_dentry);
        req->r_old_dentry_dir = old_dir;
        req->r_parent = new_dir;
        set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
        req->r_old_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_old_dentry_unless = CEPH_CAP_FILE_EXCL;
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        /* release LINK_RDCACHE on source inode (mds will lock it) */
        req->r_old_inode_drop = CEPH_CAP_LINK_SHARED;
        if (d_really_is_positive(new_dentry))
                req->r_inode_drop = drop_caps_for_unlink(d_inode(new_dentry));
        err = ceph_mdsc_do_request(mdsc, old_dir, req);
        if (!err && !req->r_reply_info.head->is_dentry) {
                /*
                 * Normally d_move() is done by fill_trace (called by
                 * do_request, above).  If there is no trace, we need
                 * to do it here.
                 */

                /* d_move screws up sibling dentries' offsets */
                ceph_dir_clear_complete(old_dir);
                ceph_dir_clear_complete(new_dir);

                d_move(old_dentry, new_dentry);

                /* ensure target dentry is invalidated, despite
                   rehashing bug in vfs_rename_dir */
                ceph_invalidate_dentry_lease(new_dentry);
        }
        ceph_mdsc_put_request(req);
        return err;
}

/*
 * Ensure a dentry lease will no longer revalidate.
 */
void ceph_invalidate_dentry_lease(struct dentry *dentry)
{
        spin_lock(&dentry->d_lock);
        ceph_dentry(dentry)->time = jiffies;
        ceph_dentry(dentry)->lease_shared_gen = 0;
        spin_unlock(&dentry->d_lock);
}

/*
 * Check if dentry lease is valid.  If not, delete the lease.  Try to
 * renew if the least is more than half up.
 */
static int dentry_lease_is_valid(struct dentry *dentry, unsigned int flags,
                                 struct inode *dir)
{
        struct ceph_dentry_info *di;
        struct ceph_mds_session *s;
        int valid = 0;
        u32 gen;
        unsigned long ttl;
        struct ceph_mds_session *session = NULL;
        u32 seq = 0;

        spin_lock(&dentry->d_lock);
        di = ceph_dentry(dentry);
        if (di && di->lease_session) {
                s = di->lease_session;
                spin_lock(&s->s_gen_ttl_lock);
                gen = s->s_cap_gen;
                ttl = s->s_cap_ttl;
                spin_unlock(&s->s_gen_ttl_lock);

                if (di->lease_gen == gen &&
                    time_before(jiffies, di->time) &&
                    time_before(jiffies, ttl)) {
                        valid = 1;
                        if (di->lease_renew_after &&
                            time_after(jiffies, di->lease_renew_after)) {
                                /*
                                 * We should renew. If we're in RCU walk mode
                                 * though, we can't do that so just return
                                 * -ECHILD.
                                 */
                                if (flags & LOOKUP_RCU) {
                                        valid = -ECHILD;
                                } else {
                                        session = ceph_get_mds_session(s);
                                        seq = di->lease_seq;
                                        di->lease_renew_after = 0;
                                        di->lease_renew_from = jiffies;
                                }
                        }
                }
        }
        spin_unlock(&dentry->d_lock);

        if (session) {
                ceph_mdsc_lease_send_msg(session, dir, dentry,
                                         CEPH_MDS_LEASE_RENEW, seq);
                ceph_put_mds_session(session);
        }
        dout("dentry_lease_is_valid - dentry %p = %d\n", dentry, valid);
        return valid;
}

/*
 * Check if directory-wide content lease/cap is valid.
 */
static int dir_lease_is_valid(struct inode *dir, struct dentry *dentry)
{
        struct ceph_inode_info *ci = ceph_inode(dir);
        struct ceph_dentry_info *di = ceph_dentry(dentry);
        int valid = 0;

        spin_lock(&ci->i_ceph_lock);
        if (atomic_read(&ci->i_shared_gen) == di->lease_shared_gen)
                valid = __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1);
        spin_unlock(&ci->i_ceph_lock);
        dout("dir_lease_is_valid dir %p v%u dentry %p v%u = %d\n",
             dir, (unsigned)atomic_read(&ci->i_shared_gen),
             dentry, (unsigned)di->lease_shared_gen, valid);
        return valid;
}

/*
 * Check if cached dentry can be trusted.
 */
static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)
{
        int valid = 0;
        struct dentry *parent;
        struct inode *dir;

        if (flags & LOOKUP_RCU) {
                parent = READ_ONCE(dentry->d_parent);
                dir = d_inode_rcu(parent);
                if (!dir)
                        return -ECHILD;
        } else {
                parent = dget_parent(dentry);
                dir = d_inode(parent);
        }

        dout("d_revalidate %p '%pd' inode %p offset %lld\n", dentry,
             dentry, d_inode(dentry), ceph_dentry(dentry)->offset);

        /* always trust cached snapped dentries, snapdir dentry */
        if (ceph_snap(dir) != CEPH_NOSNAP) {
                dout("d_revalidate %p '%pd' inode %p is SNAPPED\n", dentry,
                     dentry, d_inode(dentry));
                valid = 1;
        } else if (d_really_is_positive(dentry) &&
                   ceph_snap(d_inode(dentry)) == CEPH_SNAPDIR) {
                valid = 1;
        } else {
                valid = dentry_lease_is_valid(dentry, flags, dir);
                if (valid == -ECHILD)
                        return valid;
                if (valid || dir_lease_is_valid(dir, dentry)) {
                        if (d_really_is_positive(dentry))
                                valid = ceph_is_any_caps(d_inode(dentry));
                        else
                                valid = 1;
                }
        }

        if (!valid) {
                struct ceph_mds_client *mdsc =
                        ceph_sb_to_client(dir->i_sb)->mdsc;
                struct ceph_mds_request *req;
                int op, err;
                u32 mask;

                if (flags & LOOKUP_RCU)
                        return -ECHILD;

                op = ceph_snap(dir) == CEPH_SNAPDIR ?
                        CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_LOOKUP;
                req = ceph_mdsc_create_request(mdsc, op, USE_ANY_MDS);
                if (!IS_ERR(req)) {
                        req->r_dentry = dget(dentry);
                        req->r_num_caps = 2;
                        req->r_parent = dir;

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

                        err = ceph_mdsc_do_request(mdsc, NULL, req);
                        switch (err) {
                        case 0:
                                if (d_really_is_positive(dentry) &&
                                    d_inode(dentry) == req->r_target_inode)
                                        valid = 1;
                                break;
                        case -ENOENT:
                                if (d_really_is_negative(dentry))
                                        valid = 1;
                                /* Fallthrough */
                        default:
                                break;
                        }
                        ceph_mdsc_put_request(req);
                        dout("d_revalidate %p lookup result=%d\n",
                             dentry, err);
                }
        }

        dout("d_revalidate %p %s\n", dentry, valid ? "valid" : "invalid");
        if (valid) {
                ceph_dentry_lru_touch(dentry);
        } else {
                ceph_dir_clear_complete(dir);
        }

        if (!(flags & LOOKUP_RCU))
                dput(parent);
        return valid;
}

/*
 * Release our ceph_dentry_info.
 */
static void ceph_d_release(struct dentry *dentry)
{
        struct ceph_dentry_info *di = ceph_dentry(dentry);

        dout("d_release %p\n", dentry);
        ceph_dentry_lru_del(dentry);

        spin_lock(&dentry->d_lock);
        dentry->d_fsdata = NULL;
        spin_unlock(&dentry->d_lock);

        if (di->lease_session)
                ceph_put_mds_session(di->lease_session);
        kmem_cache_free(ceph_dentry_cachep, di);
}

/*
 * When the VFS prunes a dentry from the cache, we need to clear the
 * complete flag on the parent directory.
 *
 * Called under dentry->d_lock.
 */
static void ceph_d_prune(struct dentry *dentry)
{
        struct ceph_inode_info *dir_ci;
        struct ceph_dentry_info *di;

        dout("ceph_d_prune %pd %p\n", dentry, dentry);

        /* do we have a valid parent? */
        if (IS_ROOT(dentry))
                return;

        /* we hold d_lock, so d_parent is stable */
        dir_ci = ceph_inode(d_inode(dentry->d_parent));
        if (dir_ci->i_vino.snap == CEPH_SNAPDIR)
                return;

        /* who calls d_delete() should also disable dcache readdir */
        if (d_really_is_negative(dentry))
                return;

        /* d_fsdata does not get cleared until d_release */
        if (!d_unhashed(dentry)) {
                __ceph_dir_clear_complete(dir_ci);
                return;
        }

        /* Disable dcache readdir just in case that someone called d_drop()
         * or d_invalidate(), but MDS didn't revoke CEPH_CAP_FILE_SHARED
         * properly (dcache readdir is still enabled) */
        di = ceph_dentry(dentry);
        if (di->offset > 0 &&
            di->lease_shared_gen == atomic_read(&dir_ci->i_shared_gen))
                __ceph_dir_clear_ordered(dir_ci);
}

/*
 * read() on a dir.  This weird interface hack only works if mounted
 * with '-o dirstat'.
 */
static ssize_t ceph_read_dir(struct file *file, char __user *buf, size_t size,
                             loff_t *ppos)
{
        struct ceph_file_info *cf = file->private_data;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        int left;
        const int bufsize = 1024;

        if (!ceph_test_mount_opt(ceph_sb_to_client(inode->i_sb), DIRSTAT))
                return -EISDIR;

        if (!cf->dir_info) {
                cf->dir_info = kmalloc(bufsize, GFP_KERNEL);
                if (!cf->dir_info)
                        return -ENOMEM;
                cf->dir_info_len =
                        snprintf(cf->dir_info, bufsize,
                                "entries:   %20lld\n"
                                " files:    %20lld\n"
                                " subdirs:  %20lld\n"
                                "rentries:  %20lld\n"
                                " rfiles:   %20lld\n"
                                " rsubdirs: %20lld\n"
                                "rbytes:    %20lld\n"
                                "rctime:    %10ld.%09ld\n",
                                ci->i_files + ci->i_subdirs,
                                ci->i_files,
                                ci->i_subdirs,
                                ci->i_rfiles + ci->i_rsubdirs,
                                ci->i_rfiles,
                                ci->i_rsubdirs,
                                ci->i_rbytes,
                                (long)ci->i_rctime.tv_sec,
                                (long)ci->i_rctime.tv_nsec);
        }

        if (*ppos >= cf->dir_info_len)
                return 0;
        size = min_t(unsigned, size, cf->dir_info_len-*ppos);
        left = copy_to_user(buf, cf->dir_info + *ppos, size);
        if (left == size)
                return -EFAULT;
        *ppos += (size - left);
        return size - left;
}

/*
 * We maintain a private dentry LRU.
 *
 * FIXME: this needs to be changed to a per-mds lru to be useful.
 */
void ceph_dentry_lru_add(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_add %p %p '%pd'\n", di, dn, dn);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_add_tail(&di->lru, &mdsc->dentry_lru);
        mdsc->num_dentry++;
        spin_unlock(&mdsc->dentry_lru_lock);
}

void ceph_dentry_lru_touch(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_touch %p %p '%pd' (offset %lld)\n", di, dn, dn,
             di->offset);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_move_tail(&di->lru, &mdsc->dentry_lru);
        spin_unlock(&mdsc->dentry_lru_lock);
}

void ceph_dentry_lru_del(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_del %p %p '%pd'\n", di, dn, dn);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_del_init(&di->lru);
        mdsc->num_dentry--;
        spin_unlock(&mdsc->dentry_lru_lock);
}

/*
 * Return name hash for a given dentry.  This is dependent on
 * the parent directory's hash function.
 */
unsigned ceph_dentry_hash(struct inode *dir, struct dentry *dn)
{
        struct ceph_inode_info *dci = ceph_inode(dir);

        switch (dci->i_dir_layout.dl_dir_hash) {
        case 0: /* for backward compat */
        case CEPH_STR_HASH_LINUX:
                return dn->d_name.hash;

        default:
                return ceph_str_hash(dci->i_dir_layout.dl_dir_hash,
                                     dn->d_name.name, dn->d_name.len);
        }
}

const struct file_operations ceph_dir_fops = {
        .read = ceph_read_dir,
        .iterate = ceph_readdir,
        .llseek = ceph_dir_llseek,
        .open = ceph_open,
        .release = ceph_release,
        .unlocked_ioctl = ceph_ioctl,
        .fsync = ceph_fsync,
};

const struct file_operations ceph_snapdir_fops = {
        .iterate = ceph_readdir,
        .llseek = ceph_dir_llseek,
        .open = ceph_open,
        .release = ceph_release,
};

const struct inode_operations ceph_dir_iops = {
        .lookup = ceph_lookup,
        .permission = ceph_permission,
        .getattr = ceph_getattr,
        .setattr = ceph_setattr,
        .listxattr = ceph_listxattr,
        .get_acl = ceph_get_acl,
        .set_acl = ceph_set_acl,
        .mknod = ceph_mknod,
        .symlink = ceph_symlink,
        .mkdir = ceph_mkdir,
        .link = ceph_link,
        .unlink = ceph_unlink,
        .rmdir = ceph_unlink,
        .rename = ceph_rename,
        .create = ceph_create,
        .atomic_open = ceph_atomic_open,
};

const struct inode_operations ceph_snapdir_iops = {
        .lookup = ceph_lookup,
        .permission = ceph_permission,
        .getattr = ceph_getattr,
        .mkdir = ceph_mkdir,
        .rmdir = ceph_unlink,
        .rename = ceph_rename,
};

const struct dentry_operations ceph_dentry_ops = {
        .d_revalidate = ceph_d_revalidate,
        .d_release = ceph_d_release,
        .d_prune = ceph_d_prune,
        .d_init = ceph_d_init,
};