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ext4: check for need init flag in ext4_mb_load_buddy

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We should check for need init flag with the group's alloc_sem held, to
make sure while we are loading the buddy cache and holding a reference
to it, a file system resize can't add new blocks to same group.

The patch also drops the need init flag check in
ext4_mb_regular_allocator() because doing the check without holding
alloc_sem is racy.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
Aneesh Kumar K.V 2009-09-09 23:34:50 -04:00 committed by Theodore Ts'o
parent b6a758ec3a
commit f41c075053
1 changed files with 18 additions and 21 deletions
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39
fs/ext4/mballoc.c
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@ -1034,8 +1034,26 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
* groups mapped by the page is blocked
* till we are done with allocation
*/
repeat_load_buddy:
down_read(e4b->alloc_semp);
if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
/* we need to check for group need init flag
* with alloc_semp held so that we can be sure
* that new blocks didn't get added to the group
* when we are loading the buddy cache
*/
up_read(e4b->alloc_semp);
/*
* we need full data about the group
* to make a good selection
*/
ret = ext4_mb_init_group(sb, group);
if (ret)
return ret;
goto repeat_load_buddy;
}
/*
* the buddy cache inode stores the block bitmap
* and buddy information in consecutive blocks.
@ -2012,27 +2030,6 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
if (grp->bb_free == 0)
continue;
/*
* if the group is already init we check whether it is
* a good group and if not we don't load the buddy
*/
if (EXT4_MB_GRP_NEED_INIT(grp)) {
/*
* we need full data about the group
* to make a good selection
*/
err = ext4_mb_init_group(sb, group);
if (err)
goto out;
}
/*
* If the particular group doesn't satisfy our
* criteria we continue with the next group
*/
if (!ext4_mb_good_group(ac, group, cr))
continue;
err = ext4_mb_load_buddy(sb, group, &e4b);
if (err)
goto out;