From: Maxim P. <MPa...@pa...> - 2013-08-12 16:40:02
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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 date to the hole soon. Signed-off-by: Maxim Patlasov <mpa...@pa...> --- fs/fuse/file.c | 53 ++++++++++++++++++++++++++++++++++++++++++++--------- 1 files changed, 44 insertions(+), 9 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index d1715b3..2b18c4b 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -344,6 +344,31 @@ static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) return found; } +static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from, + pgoff_t idx_to) +{ + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_req *req; + bool found = false; + + spin_lock(&fc->lock); + list_for_each_entry(req, &fi->writepages, writepages_entry) { + pgoff_t curr_index; + + BUG_ON(req->inode != inode); + curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT; + if (!(idx_from >= curr_index + req->num_pages || + idx_to < curr_index)) { + found = true; + break; + } + } + spin_unlock(&fc->lock); + + return found; +} + /* * Wait for page writeback to be completed. * @@ -358,6 +383,19 @@ static int fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index) return 0; } +static void fuse_wait_on_writeback(struct inode *inode, pgoff_t start, + size_t bytes) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + pgoff_t idx_from, idx_to; + + idx_from = start >> PAGE_CACHE_SHIFT; + idx_to = (start + bytes - 1) >> PAGE_CACHE_SHIFT; + + wait_event(fi->page_waitq, + !fuse_range_is_writeback(inode, idx_from, idx_to)); +} + static int fuse_flush(struct file *file, fl_owner_t id) { struct inode *inode = file_inode(file); @@ -2478,8 +2516,11 @@ 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) { + truncate_pagecache_range(inode, offset, + offset + length - 1); + fuse_wait_on_writeback(inode, offset, length); + } } req = fuse_get_req_nopages(fc); @@ -2508,17 +2549,11 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, if (!(mode & FALLOC_FL_KEEP_SIZE)) fuse_write_update_size(inode, offset + length); - if (mode & FALLOC_FL_PUNCH_HOLE) - truncate_pagecache_range(inode, offset, offset + length - 1); - 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; } |