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