From: Eryu Guan Subject: [PATCH] ext4: no need to remove extent if len is 0 in ext4_es_remove_extent() Date: Fri, 22 Feb 2013 13:34:03 +0800 Message-ID: <1361511243-2458-1-git-send-email-guaneryu@gmail.com> Cc: Eryu Guan , Zheng Liu , "Theodore Ts'o" To: linux-ext4@vger.kernel.org Return-path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:34742 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750866Ab3BVFeg (ORCPT ); Fri, 22 Feb 2013 00:34:36 -0500 Received: by mail-pa0-f49.google.com with SMTP id kp6so260422pab.36 for ; Thu, 21 Feb 2013 21:34:35 -0800 (PST) Sender: linux-ext4-owner@vger.kernel.org List-ID: len is 0 means no extent needs to be removed, so return immediately. Otherwise it could trigger the following BUG_ON() 436 end = offset + len - 1; 437 BUG_ON(end < offset); This could be reproduced by a simple truncate(1) command by an unprivileged user truncate -s $(($((2**32 - 1)) * 4096)) /mnt/ext4/testfile The same is true for __es_insert_extent(). Patched kernel passed xfstests regression test. Also remove comments about EXT4_I(inode)->i_es_lock, this rwlock isn't hold by callers. Cc: Zheng Liu Cc: "Theodore Ts'o" Signed-off-by: Eryu Guan --- fs/ext4/extents_status.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c index 564d981..3ac09ca 100644 --- a/fs/ext4/extents_status.c +++ b/fs/ext4/extents_status.c @@ -328,6 +328,9 @@ static int __es_insert_extent(struct ext4_es_tree *tree, ext4_lblk_t offset, struct extent_status *es; ext4_lblk_t end = offset + len - 1; + if (!len) + return 0; + BUG_ON(end < offset); es = tree->cache_es; if (es && offset == (extent_status_end(es) + 1)) { @@ -386,7 +389,6 @@ out: /* * ext4_es_insert_extent() adds a space to a delayed extent tree. - * Caller holds inode->i_es_lock. * * ext4_es_insert_extent is called by ext4_da_write_begin and * ext4_es_remove_extent. @@ -415,7 +417,6 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t offset, /* * ext4_es_remove_extent() removes a space from a delayed extent tree. - * Caller holds inode->i_es_lock. * * Return 0 on success, error code on failure. */ @@ -433,6 +434,9 @@ int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t offset, es_debug("remove [%u/%u) from extent status tree of inode %lu\n", offset, len, inode->i_ino); + if (!len) + return err; + end = offset + len - 1; BUG_ON(end < offset); write_lock(&EXT4_I(inode)->i_es_lock); -- 1.8.1.2