3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx>
commit bde52788bdb755b9e4b75db6c434f30e32a0ca0b upstream.
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@xxxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/fuse/file.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2485,8 +2485,15 @@ static long fuse_file_fallocate(struct f
if (lock_inode) {
mutex_lock(&inode->i_mutex);
- if (mode & FALLOC_FL_PUNCH_HOLE)
- fuse_set_nowrite(inode);
+ if (mode & FALLOC_FL_PUNCH_HOLE) {
+ loff_t endbyte = offset + length - 1;
+ err = filemap_write_and_wait_range(inode->i_mapping,
+ offset, endbyte);
+ if (err)
+ goto out;
+
+ fuse_sync_writes(inode);
+ }
}
req = fuse_get_req_nopages(fc);
@@ -2521,11 +2528,8 @@ static long fuse_file_fallocate(struct f
fuse_invalidate_attr(inode);
out:
- if (lock_inode) {
- if (mode & FALLOC_FL_PUNCH_HOLE)
- fuse_release_nowrite(inode);
+ if (lock_inode)
mutex_unlock(&inode->i_mutex);
- }
return err;
}
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