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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
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parent
272b98c645
commit
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1 changed files with 10 additions and 6 deletions
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@ -2484,8 +2484,15 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
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if (lock_inode) {
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mutex_lock(&inode->i_mutex);
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if (mode & FALLOC_FL_PUNCH_HOLE)
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fuse_set_nowrite(inode);
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if (mode & FALLOC_FL_PUNCH_HOLE) {
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loff_t endbyte = offset + length - 1;
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err = filemap_write_and_wait_range(inode->i_mapping,
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offset, endbyte);
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if (err)
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goto out;
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fuse_sync_writes(inode);
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}
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}
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req = fuse_get_req_nopages(fc);
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@ -2520,11 +2527,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
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fuse_invalidate_attr(inode);
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out:
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if (lock_inode) {
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if (mode & FALLOC_FL_PUNCH_HOLE)
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fuse_release_nowrite(inode);
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if (lock_inode)
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mutex_unlock(&inode->i_mutex);
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}
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return err;
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}
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