From 25d14f983f70ddbeb15fa2d0f32f6b70bca42a15 Mon Sep 17 00:00:00 2001 From: Amit Arora Date: Thu, 24 May 2007 13:04:13 -0400 Subject: ext4: Extent overlap bugfix 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. Signed-off-by: Amit Arora Signed-off-by: "Theodore Ts'o" --- fs/ext4/extents.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 58 insertions(+), 2 deletions(-) (limited to 'fs/ext4') diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 1630317817b8..03c777abf01f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1127,6 +1127,55 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, return 0; } +/* + * 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 @@ -2031,7 +2080,15 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, /* 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, struct inode *inode, 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); -- cgit v1.2.3-59-g8ed1b