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authorMaxim Patlasov <MPatlasov@parallels.com>2013-09-13 11:19:54 -0400
committerMiklos Szeredi <mszeredi@suse.cz>2013-09-18 08:19:59 -0400
commitbde52788bdb755b9e4b75db6c434f30e32a0ca0b (patch)
tree98ce29d7755630e5e6060e3357a79dd9e02e5088 /fs/fuse
parent272b98c6455f00884f0350f775c5342358ebb73f (diff)
fuse: wait for writeback in fuse_file_fallocate()
The patch fixes a race between mmap-ed write and fallocate(PUNCH_HOLE): 1) An user makes a page dirty via mmap-ed write. 2) The user performs fallocate(2) with mode == PUNCH_HOLE|KEEP_SIZE and <offset, size> covering the page. 3) Before truncate_pagecache_range call from fuse_file_fallocate, the page goes to write-back. The page is fully processed by fuse_writepage (including end_page_writeback on the page), but fuse_flush_writepages did nothing because fi->writectr < 0. 4) truncate_pagecache_range is called and fuse_file_fallocate is finishing by calling fuse_release_nowrite. The latter triggers processing queued write-back request which will write stale data to the hole soon. Changed in v2 (thanks to Brian for suggestion): - Do not truncate page cache until FUSE_FALLOCATE succeeded. Otherwise, we can end up in returning -ENOTSUPP while user data is already punched from page cache. Use filemap_write_and_wait_range() instead. Changed in v3 (thanks to Miklos for suggestion): - fuse_wait_on_writeback() is prone to livelocks; use fuse_set_nowrite() instead. So far as we need a dirty-page barrier only, fuse_sync_writes() should be enough. - rebased to for-linus branch of fuse.git Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/file.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index d409deafc67b..f9f07c4fa517 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2484,8 +2484,15 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
2484 2484
2485 if (lock_inode) { 2485 if (lock_inode) {
2486 mutex_lock(&inode->i_mutex); 2486 mutex_lock(&inode->i_mutex);
2487 if (mode & FALLOC_FL_PUNCH_HOLE) 2487 if (mode & FALLOC_FL_PUNCH_HOLE) {
2488 fuse_set_nowrite(inode); 2488 loff_t endbyte = offset + length - 1;
2489 err = filemap_write_and_wait_range(inode->i_mapping,
2490 offset, endbyte);
2491 if (err)
2492 goto out;
2493
2494 fuse_sync_writes(inode);
2495 }
2489 } 2496 }
2490 2497
2491 req = fuse_get_req_nopages(fc); 2498 req = fuse_get_req_nopages(fc);
@@ -2520,11 +2527,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
2520 fuse_invalidate_attr(inode); 2527 fuse_invalidate_attr(inode);
2521 2528
2522out: 2529out:
2523 if (lock_inode) { 2530 if (lock_inode)
2524 if (mode & FALLOC_FL_PUNCH_HOLE)
2525 fuse_release_nowrite(inode);
2526 mutex_unlock(&inode->i_mutex); 2531 mutex_unlock(&inode->i_mutex);
2527 }
2528 2532
2529 return err; 2533 return err;
2530} 2534}