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ext4: teach ext4_ext_find_extent() to realloc path if necessary
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This adds additional safety in case for some reason we end reusing a
path structure which isn't big enough for current depth of the inode.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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tytso committed Sep 1, 2014
1 parent b7ea89a commit 10809df
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Showing 2 changed files with 11 additions and 10 deletions.
1 change: 1 addition & 0 deletions fs/ext4/ext4_extents.h
Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,7 @@ find_ext4_extent_tail(struct ext4_extent_header *eh)
struct ext4_ext_path {
ext4_fsblk_t p_block;
__u16 p_depth;
__u16 p_maxdepth;
struct ext4_extent *p_ext;
struct ext4_extent_idx *p_idx;
struct ext4_extent_header *p_hdr;
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20 changes: 10 additions & 10 deletions fs/ext4/extents.c
Original file line number Diff line number Diff line change
Expand Up @@ -869,14 +869,20 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
eh = ext_inode_hdr(inode);
depth = ext_depth(inode);

if (path)
if (path) {
ext4_ext_drop_refs(path);
else {
if (depth > path[0].p_maxdepth) {
kfree(path);
*orig_path = path = NULL;
}
}
if (!path) {
/* account possible depth increase */
path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
GFP_NOFS);
if (unlikely(!path))
return ERR_PTR(-ENOMEM);
path[0].p_maxdepth = depth + 1;
}
path[0].p_hdr = eh;
path[0].p_bh = NULL;
Expand Down Expand Up @@ -1820,6 +1826,7 @@ static void ext4_ext_try_to_merge_up(handle_t *handle,
sizeof(struct ext4_extent_idx);
s += sizeof(struct ext4_extent_header);

path[1].p_maxdepth = path[0].p_maxdepth;
memcpy(path[0].p_hdr, path[1].p_hdr, s);
path[0].p_depth = 0;
path[0].p_ext = EXT_FIRST_EXTENT(path[0].p_hdr) +
Expand Down Expand Up @@ -2150,12 +2157,6 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
/* find extent for this block */
down_read(&EXT4_I(inode)->i_data_sem);

if (path && ext_depth(inode) != depth) {
/* depth was changed. we have to realloc path */
kfree(path);
path = NULL;
}

path = ext4_ext_find_extent(inode, block, &path, 0);
if (IS_ERR(path)) {
up_read(&EXT4_I(inode)->i_data_sem);
Expand All @@ -2173,7 +2174,6 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
}
ex = path[depth].p_ext;
next = ext4_ext_next_allocated_block(path);
ext4_ext_drop_refs(path);

flags = 0;
exists = 0;
Expand Down Expand Up @@ -2897,7 +2897,7 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
ext4_journal_stop(handle);
return -ENOMEM;
}
path[0].p_depth = depth;
path[0].p_maxdepth = path[0].p_depth = depth;
path[0].p_hdr = ext_inode_hdr(inode);
i = 0;

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