fs/9p/vfs_addr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/9p/vfs_addr.c
   4  *
   5  * This file contians vfs address (mmap) ops for 9P2000.
   6  *
   7  *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
   8  *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/errno.h>
  13 #include <linux/fs.h>
  14 #include <linux/file.h>
  15 #include <linux/stat.h>
  16 #include <linux/string.h>
  17 #include <linux/inet.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/idr.h>
  20 #include <linux/sched.h>
  21 #include <linux/uio.h>
  22 #include <linux/bvec.h>
  23 #include <net/9p/9p.h>
  24 #include <net/9p/client.h>
  25
  26 #include "v9fs.h"
  27 #include "v9fs_vfs.h"
  28 #include "cache.h"
  29 #include "fid.h"
  30
  31 /**
  32  * v9fs_fid_readpage - read an entire page in from 9P
  33  * @data: Opaque pointer to the fid being read
  34  * @page: structure to page
  35  *
  36  */
  37 static int v9fs_fid_readpage(void *data, struct page *page)
  38 {
  39         struct p9_fid *fid = data;
  40         struct inode *inode = page->mapping->host;
  41         struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
  42         struct iov_iter to;
  43         int retval, err;
  44
  45         p9_debug(P9_DEBUG_VFS, "\n");
  46
  47         BUG_ON(!PageLocked(page));
  48
  49         retval = v9fs_readpage_from_fscache(inode, page);
  50         if (retval == 0)
  51                 return retval;
  52
  53         iov_iter_bvec(&to, READ, &bvec, 1, PAGE_SIZE);
  54
  55         retval = p9_client_read(fid, page_offset(page), &to, &err);
  56         if (err) {
  57                 v9fs_uncache_page(inode, page);
  58                 retval = err;
  59                 goto done;
  60         }
  61
  62         zero_user(page, retval, PAGE_SIZE - retval);
  63         flush_dcache_page(page);
  64         SetPageUptodate(page);
  65
  66         v9fs_readpage_to_fscache(inode, page);
  67         retval = 0;
  68
  69 done:
  70         unlock_page(page);
  71         return retval;
  72 }
  73
  74 /**
  75  * v9fs_vfs_readpage - read an entire page in from 9P
  76  *
  77  * @filp: file being read
  78  * @page: structure to page
  79  *
  80  */
  81
  82 static int v9fs_vfs_readpage(struct file *filp, struct page *page)
  83 {
  84         return v9fs_fid_readpage(filp->private_data, page);
  85 }
  86
  87 /**
  88  * v9fs_vfs_readpages - read a set of pages from 9P
  89  *
  90  * @filp: file being read
  91  * @mapping: the address space
  92  * @pages: list of pages to read
  93  * @nr_pages: count of pages to read
  94  *
  95  */
  96
  97 static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
  98                              struct list_head *pages, unsigned nr_pages)
  99 {
 100         int ret = 0;
 101         struct inode *inode;
 102
 103         inode = mapping->host;
 104         p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
 105
 106         ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
 107         if (ret == 0)
 108                 return ret;
 109
 110         ret = read_cache_pages(mapping, pages, v9fs_fid_readpage,
 111                         filp->private_data);
 112         p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
 113         return ret;
 114 }
 115
 116 /**
 117  * v9fs_release_page - release the private state associated with a page
 118  * @page: The page to be released
 119  * @gfp: The caller's allocation restrictions
 120  *
 121  * Returns 1 if the page can be released, false otherwise.
 122  */
 123
 124 static int v9fs_release_page(struct page *page, gfp_t gfp)
 125 {
 126         if (PagePrivate(page))
 127                 return 0;
 128         return v9fs_fscache_release_page(page, gfp);
 129 }
 130
 131 /**
 132  * v9fs_invalidate_page - Invalidate a page completely or partially
 133  * @page: The page to be invalidated
 134  * @offset: offset of the invalidated region
 135  * @length: length of the invalidated region
 136  */
 137
 138 static void v9fs_invalidate_page(struct page *page, unsigned int offset,
 139                                  unsigned int length)
 140 {
 141         /*
 142          * If called with zero offset, we should release
 143          * the private state assocated with the page
 144          */
 145         if (offset == 0 && length == PAGE_SIZE)
 146                 v9fs_fscache_invalidate_page(page);
 147 }
 148
 149 static int v9fs_vfs_writepage_locked(struct page *page)
 150 {
 151         struct inode *inode = page->mapping->host;
 152         struct v9fs_inode *v9inode = V9FS_I(inode);
 153         loff_t size = i_size_read(inode);
 154         struct iov_iter from;
 155         struct bio_vec bvec;
 156         int err, len;
 157
 158         if (page->index == size >> PAGE_SHIFT)
 159                 len = size & ~PAGE_MASK;
 160         else
 161                 len = PAGE_SIZE;
 162
 163         bvec.bv_page = page;
 164         bvec.bv_offset = 0;
 165         bvec.bv_len = len;
 166         iov_iter_bvec(&from, WRITE, &bvec, 1, len);
 167
 168         /* We should have writeback_fid always set */
 169         BUG_ON(!v9inode->writeback_fid);
 170
 171         set_page_writeback(page);
 172
 173         p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
 174
 175         end_page_writeback(page);
 176         return err;
 177 }
 178
 179 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 180 {
 181         int retval;
 182
 183         p9_debug(P9_DEBUG_VFS, "page %p\n", page);
 184
 185         retval = v9fs_vfs_writepage_locked(page);
 186         if (retval < 0) {
 187                 if (retval == -EAGAIN) {
 188                         redirty_page_for_writepage(wbc, page);
 189                         retval = 0;
 190                 } else {
 191                         SetPageError(page);
 192                         mapping_set_error(page->mapping, retval);
 193                 }
 194         } else
 195                 retval = 0;
 196
 197         unlock_page(page);
 198         return retval;
 199 }
 200
 201 /**
 202  * v9fs_launder_page - Writeback a dirty page
 203  * @page: The page to be cleaned up
 204  *
 205  * Returns 0 on success.
 206  */
 207
 208 static int v9fs_launder_page(struct page *page)
 209 {
 210         int retval;
 211         struct inode *inode = page->mapping->host;
 212
 213         v9fs_fscache_wait_on_page_write(inode, page);
 214         if (clear_page_dirty_for_io(page)) {
 215                 retval = v9fs_vfs_writepage_locked(page);
 216                 if (retval)
 217                         return retval;
 218         }
 219         return 0;
 220 }
 221
 222 /**
 223  * v9fs_direct_IO - 9P address space operation for direct I/O
 224  * @iocb: target I/O control block
 225  * @iter: The data/buffer to use
 226  *
 227  * The presence of v9fs_direct_IO() in the address space ops vector
 228  * allowes open() O_DIRECT flags which would have failed otherwise.
 229  *
 230  * In the non-cached mode, we shunt off direct read and write requests before
 231  * the VFS gets them, so this method should never be called.
 232  *
 233  * Direct IO is not 'yet' supported in the cached mode. Hence when
 234  * this routine is called through generic_file_aio_read(), the read/write fails
 235  * with an error.
 236  *
 237  */
 238 static ssize_t
 239 v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 240 {
 241         struct file *file = iocb->ki_filp;
 242         loff_t pos = iocb->ki_pos;
 243         ssize_t n;
 244         int err = 0;
 245         if (iov_iter_rw(iter) == WRITE) {
 246                 n = p9_client_write(file->private_data, pos, iter, &err);
 247                 if (n) {
 248                         struct inode *inode = file_inode(file);
 249                         loff_t i_size = i_size_read(inode);
 250                         if (pos + n > i_size)
 251                                 inode_add_bytes(inode, pos + n - i_size);
 252                 }
 253         } else {
 254                 n = p9_client_read(file->private_data, pos, iter, &err);
 255         }
 256         return n ? n : err;
 257 }
 258
 259 static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 260                             loff_t pos, unsigned len, unsigned flags,
 261                             struct page **pagep, void **fsdata)
 262 {
 263         int retval = 0;
 264         struct page *page;
 265         struct v9fs_inode *v9inode;
 266         pgoff_t index = pos >> PAGE_SHIFT;
 267         struct inode *inode = mapping->host;
 268
 269
 270         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 271
 272         v9inode = V9FS_I(inode);
 273 start:
 274         page = grab_cache_page_write_begin(mapping, index, flags);
 275         if (!page) {
 276                 retval = -ENOMEM;
 277                 goto out;
 278         }
 279         BUG_ON(!v9inode->writeback_fid);
 280         if (PageUptodate(page))
 281                 goto out;
 282
 283         if (len == PAGE_SIZE)
 284                 goto out;
 285
 286         retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 287         put_page(page);
 288         if (!retval)
 289                 goto start;
 290 out:
 291         *pagep = page;
 292         return retval;
 293 }
 294
 295 static int v9fs_write_end(struct file *filp, struct address_space *mapping,
 296                           loff_t pos, unsigned len, unsigned copied,
 297                           struct page *page, void *fsdata)
 298 {
 299         loff_t last_pos = pos + copied;
 300         struct inode *inode = page->mapping->host;
 301
 302         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 303
 304         if (!PageUptodate(page)) {
 305                 if (unlikely(copied < len)) {
 306                         copied = 0;
 307                         goto out;
 308                 } else if (len == PAGE_SIZE) {
 309                         SetPageUptodate(page);
 310                 }
 311         }
 312         /*
 313          * No need to use i_size_read() here, the i_size
 314          * cannot change under us because we hold the i_mutex.
 315          */
 316         if (last_pos > inode->i_size) {
 317                 inode_add_bytes(inode, last_pos - inode->i_size);
 318                 i_size_write(inode, last_pos);
 319         }
 320         set_page_dirty(page);
 321 out:
 322         unlock_page(page);
 323         put_page(page);
 324
 325         return copied;
 326 }
 327
 328
 329 const struct address_space_operations v9fs_addr_operations = {
 330         .readpage = v9fs_vfs_readpage,
 331         .readpages = v9fs_vfs_readpages,
 332         .set_page_dirty = __set_page_dirty_nobuffers,
 333         .writepage = v9fs_vfs_writepage,
 334         .write_begin = v9fs_write_begin,
 335         .write_end = v9fs_write_end,
 336         .releasepage = v9fs_release_page,
 337         .invalidatepage = v9fs_invalidate_page,
 338         .launder_page = v9fs_launder_page,
 339         .direct_IO = v9fs_direct_IO,
 340 };