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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 <aarora@in.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Amit Arora 2007-05-24 13:04:13 -04:00 committed by Theodore Ts'o
parent 8a9dc94498
commit 25d14f983f
2 changed files with 59 additions and 2 deletions
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60
fs/ext4/extents.c
View File

@ -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);

1
include/linux/ext4_fs_extents.h
View File

@ -190,6 +190,7 @@ ext4_ext_invalidate_cache(struct inode *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 *);