From bde52788bdb755b9e4b75db6c434f30e32a0ca0b Mon Sep 17 00:00:00 2001 From: Maxim Patlasov Date: Fri, 13 Sep 2013 19:19:54 +0400 Subject: [PATCH] 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 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 Signed-off-by: Miklos Szeredi Cc: stable@vger.kernel.org --- fs/fuse/file.c | 16 ++++++++++------ 1 file 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, 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); @@ -2520,11 +2527,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, 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; } -- 2.34.1