From: "Amit K. Arora" Subject: Re: [PATCH 1/1 version2] Extent overlap bugfix in ext4 Date: Thu, 4 Jan 2007 22:53:29 +0530 Message-ID: <20070104172329.GA23612@amitarora.in.ibm.com> References: <20070102090909.GA20503@amitarora.in.ibm.com> <1167788128.4197.17.camel@dyn9047017103.beaverton.ibm.com> <20070103060601.GB5343@amitarora.in.ibm.com> <20070104085407.GC5345@amitarora.in.ibm.com> <20070104112707.GB15920@amitarora.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mingming Cao , linux-ext4@vger.kernel.org, suparna@in.ibm.com Return-path: Received: from e31.co.us.ibm.com ([32.97.110.149]:57438 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965045AbXADRXo (ORCPT ); Thu, 4 Jan 2007 12:23:44 -0500 Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e31.co.us.ibm.com (8.13.8/8.12.11) with ESMTP id l04HNd8x018816 for ; Thu, 4 Jan 2007 12:23:39 -0500 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by westrelay02.boulder.ibm.com (8.13.6/8.13.6/NCO v8.1.1) with ESMTP id l04HNdLK412646 for ; Thu, 4 Jan 2007 10:23:39 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l04HNcE4008485 for ; Thu, 4 Jan 2007 10:23:39 -0700 To: Alex Tomas Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu, Jan 04, 2007 at 02:37:40PM +0300, Alex Tomas (AT) wrote: > >>>>> Amit K Arora (AKA) writes: > AT> I'm also not sure we need ext4_ext_find_extent() here. > AKA> Do you mean ext4_ext_next_allocated_block() above ? We anyhow have to > AKA> call find_extent() to get the possible neighbouring extent. > AT> no, I exactly meant ext4_ext_find_extent(). it's expensive > AT> compared to ext4_ext_next_allocated_block(). > AT> and if I understand right, you don't need whole extent, you > AT> just need to know next allocated block, which can be retrieved > AT> from index even. this is what ext4_ext_next_allocated_block() does. Ok, Thanks! Here is the updated patch. Signed-off-by: Amit Arora --- fs/ext4/extents.c | 67 ++++++++++++++++++++++++++++++++++++++-- include/linux/ext4_fs_extents.h | 1 2 files changed, 66 insertions(+), 2 deletions(-) Index: linux-2.6.19.prealloc/fs/ext4/extents.c =================================================================== --- linux-2.6.19.prealloc.orig/fs/ext4/extents.c +++ linux-2.6.19.prealloc/fs/ext4/extents.c @@ -1119,6 +1119,43 @@ ext4_can_extents_be_merged(struct inode } /* + * ext4_ext_check_overlap: + * check if a portion of the "newext" extent overlaps with an + * existing extent. + * + * If there is an overlap discovered, it returns the (logical) block + * number of the first block in the next extent (the existing extent + * which covers few of the new requested blocks) + * 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 int depth, b1, len1, b2; + + 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; + } + + if (b1 + len1 > b2) + return b2; +out: + return 0; +} + +/* * ext4_ext_insert_extent: * tries to merge requsted extent into the existing extent or * inserts requested extent as new one into the tree, @@ -1133,12 +1170,25 @@ int ext4_ext_insert_extent(handle_t *han struct ext4_extent *nearex; /* nearest extent */ struct ext4_ext_path *npath = NULL; int depth, len, err, next; + unsigned int oblock; BUG_ON(newext->ee_len == 0); depth = ext_depth(inode); ex = path[depth].p_ext; BUG_ON(path[depth].p_hdr == NULL); + /* check for overlap */ + oblock = ext4_ext_check_overlap(inode, newext, path); + if (oblock) { + printk(KERN_ERR "ERROR: newext=%u/%u overlaps with an " + "existing extent, which starts with %u\n", + le32_to_cpu(newext->ee_block), + le16_to_cpu(newext->ee_len), + oblock); + ext4_ext_show_leaf(inode, path); + BUG(); + } + /* try to insert block into found extent and return */ if (ex && ext4_can_extents_be_merged(inode, ex, newext)) { ext_debug("append %d block to %d:%d (from %llu)\n", @@ -1984,6 +2034,10 @@ int ext4_ext_get_blocks(handle_t *handle */ if (ee_len > EXT_MAX_LEN) goto out2; + + if (iblock < ee_block && iblock + max_blocks >= ee_block) + allocated = ee_block - iblock; + /* if found extent covers block, simply return it */ if (iblock >= ee_block && iblock < ee_block + ee_len) { newblock = iblock - ee_block + ee_start; @@ -2016,7 +2070,17 @@ 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); + if (!allocated) { + newex.ee_len = cpu_to_le16(max_blocks); + allocated = ext4_ext_check_overlap(inode, &newex, path); + if (allocated) + allocated = allocated - iblock; + else + allocated = max_blocks; + } newblock = ext4_new_blocks(handle, inode, goal, &allocated, &err); if (!newblock) goto out2; @@ -2024,7 +2088,6 @@ 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-2.6.19.prealloc/include/linux/ext4_fs_extents.h =================================================================== --- linux-2.6.19.prealloc.orig/include/linux/ext4_fs_extents.h +++ linux-2.6.19.prealloc/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 *);