From: "Amit K. Arora" Subject: [PATCH 3/5][TAKE3] ext4: Extent overlap bugfix Date: Wed, 16 May 2007 01:43:30 +0530 Message-ID: <20070515201330.GC5834@amitarora.in.ibm.com> References: <20070329101010.7a2b8783.akpm@linux-foundation.org> <20070330071417.GI355@devserv.devel.redhat.com> <20070417125514.GA7574@amitarora.in.ibm.com> <20070418130600.GW5967@schatzie.adilger.int> <20070420135146.GA21352@amitarora.in.ibm.com> <20070420145918.GY355@devserv.devel.redhat.com> <20070424121632.GA10136@amitarora.in.ibm.com> <20070426175056.GA25321@amitarora.in.ibm.com> <20070515193722.GA3487@amitarora.in.ibm.com> <20070515195421.GA2948@amitarora.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, xfs@oss.sgi.com, suparna@in.ibm.com, cmm@us.ibm.com To: torvalds@osdl.org, akpm@linux-foundation.org Return-path: Received: from e31.co.us.ibm.com ([32.97.110.149]:55229 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754550AbXEOUN1 (ORCPT ); Tue, 15 May 2007 16:13:27 -0400 Content-Disposition: inline In-Reply-To: <20070515195421.GA2948@amitarora.in.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This patch adds a check for overlap of extents and cuts short the new extent to be inserted, if there is a chance of overlap. Changelog: --------- Note: The changes below are from the initial post (dated 26th April, 2007) and _not_ from TAKE2. The only difference from TAKE2 is the kernel version on which this patch is based. TAKE2 was based on 2.6.21 and this is based on 2.6.22-rc1. As suggested by Andrew, a check for wrap though zero has been added. Here is the new patch: Signed-off-by: Amit Arora --- fs/ext4/extents.c | 60 ++++++++++++++++++++++++++++++++++++++-- include/linux/ext4_fs_extents.h | 1 2 files changed, 59 insertions(+), 2 deletions(-) Index: linux-2.6.22-rc1/fs/ext4/extents.c =================================================================== --- linux-2.6.22-rc1.orig/fs/ext4/extents.c +++ linux-2.6.22-rc1/fs/ext4/extents.c @@ -1128,6 +1128,55 @@ ext4_can_extents_be_merged(struct inode } /* + * check if a portion of the "newext" extent overlaps with an + * existing extent. + * + * If there is an overlap discovered, it updates the length of the newext + * such that there will be no overlap, and then returns 1. + * If there is no overlap found, it returns 0. + */ +unsigned int ext4_ext_check_overlap(struct inode *inode, + struct ext4_extent *newext, + struct ext4_ext_path *path) +{ + unsigned long b1, b2; + unsigned int depth, len1; + unsigned int ret = 0; + + b1 = le32_to_cpu(newext->ee_block); + len1 = le16_to_cpu(newext->ee_len); + depth = ext_depth(inode); + if (!path[depth].p_ext) + goto out; + b2 = le32_to_cpu(path[depth].p_ext->ee_block); + + /* + * get the next allocated block if the extent in the path + * is before the requested block(s) + */ + if (b2 < b1) { + b2 = ext4_ext_next_allocated_block(path); + if (b2 == EXT_MAX_BLOCK) + goto out; + } + + /* check for wrap through zero */ + if (b1 + len1 < b1) { + len1 = EXT_MAX_BLOCK - b1; + newext->ee_len = cpu_to_le16(len1); + ret = 1; + } + + /* check for overlap */ + if (b1 + len1 > b2) { + newext->ee_len = cpu_to_le16(b2 - b1); + ret = 1; + } +out: + return ret; +} + +/* * ext4_ext_insert_extent: * tries to merge requsted extent into the existing extent or * inserts requested extent as new one into the tree, @@ -2031,7 +2080,15 @@ int ext4_ext_get_blocks(handle_t *handle /* allocate new block */ goal = ext4_ext_find_goal(inode, path, iblock); - allocated = max_blocks; + + /* Check if we can really insert (iblock)::(iblock+max_blocks) extent */ + newex.ee_block = cpu_to_le32(iblock); + newex.ee_len = cpu_to_le16(max_blocks); + err = ext4_ext_check_overlap(inode, &newex, path); + if (err) + allocated = le16_to_cpu(newex.ee_len); + else + allocated = max_blocks; newblock = ext4_new_blocks(handle, inode, goal, &allocated, &err); if (!newblock) goto out2; @@ -2039,7 +2096,6 @@ int ext4_ext_get_blocks(handle_t *handle goal, newblock, allocated); /* try to insert new extent into found leaf and return */ - newex.ee_block = cpu_to_le32(iblock); ext4_ext_store_pblock(&newex, newblock); newex.ee_len = cpu_to_le16(allocated); err = ext4_ext_insert_extent(handle, inode, path, &newex); Index: linux-2.6.22-rc1/include/linux/ext4_fs_extents.h =================================================================== --- linux-2.6.22-rc1.orig/include/linux/ext4_fs_extents.h +++ linux-2.6.22-rc1/include/linux/ext4_fs_extents.h @@ -190,6 +190,7 @@ ext4_ext_invalidate_cache(struct inode * extern int ext4_extent_tree_init(handle_t *, struct inode *); extern int ext4_ext_calc_credits_for_insert(struct inode *, struct ext4_ext_path *); +extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, struct ext4_ext_path *); extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *); extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *); extern struct ext4_ext_path * ext4_ext_find_extent(struct inode *, int, struct ext4_ext_path *);