2015-10-15 00:23:07

by Daeho Jeong

Subject: [PATCH] ext4: fix xfstest generic/269 double revoked buffer bug

When you repeatly execute xfstest generic/269 with bigalloc_1k option
enabled using the below command:

"./kvm-xfstests -c bigalloc_1k -m nodelalloc -C 1000 generic/269"

you can easily see the below bug message.

"JBD2 unexpected failure: jbd2_journal_revoke: !buffer_revoked(bh);"

This means that an already revoked buffer is erroneously revoked again
and it is caused by doing revoke for the buffer at the wrong position
in ext4_free_blocks(). We need to re-position the buffer revoke
procedure for an unspecified buffer after checking the cluster boundary
for bigalloc option. If not, some part of the cluster can be doubly
revoked.

Signed-off-by: Daeho Jeong <[email protected]>
---
fs/ext4/mballoc.c | 33 ++++++++++++++++++---------------
1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 34b610e..abea276 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4682,22 +4682,11 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
ext4_debug("freeing block %llu\n", block);
trace_ext4_free_blocks(inode, block, count, flags);

- if (flags & EXT4_FREE_BLOCKS_FORGET) {
- struct buffer_head *tbh = bh;
- int i;
-
- BUG_ON(bh && (count > 1));
+ if (bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
+ BUG_ON(count > 1);

- for (i = 0; i < count; i++) {
- cond_resched();
- if (!bh)
- tbh = sb_find_get_block(inode->i_sb,
- block + i);
- if (!tbh)
- continue;
- ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
- inode, tbh, block + i);
- }
+ ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
+ inode, bh, block);
}

/*
@@ -4742,6 +4731,20 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
count += sbi->s_cluster_ratio - overflow;
}

+ if (!bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
+ int i;
+
+ for (i = 0; i < count; i++) {
+ cond_resched();
+ bh = sb_find_get_block(inode->i_sb,
+ block + i);
+ if (!bh)
+ continue;
+ ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
+ inode, bh, block + i);
+ }
+ }
+
do_more:
overflow = 0;
ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
--
1.7.9.5

2015-10-18 02:30:27

by Theodore Ts'o

Subject: Re: [PATCH] ext4: fix xfstest generic/269 double revoked buffer bug

On Thu, Oct 15, 2015 at 09:23:18AM +0900, Daeho Jeong wrote:
> When you repeatly execute xfstest generic/269 with bigalloc_1k option
> enabled using the below command:
>
> "./kvm-xfstests -c bigalloc_1k -m nodelalloc -C 1000 generic/269"
>
> you can easily see the below bug message.
>
> "JBD2 unexpected failure: jbd2_journal_revoke: !buffer_revoked(bh);"
>
> This means that an already revoked buffer is erroneously revoked again
> and it is caused by doing revoke for the buffer at the wrong position
> in ext4_free_blocks(). We need to re-position the buffer revoke
> procedure for an unspecified buffer after checking the cluster boundary
> for bigalloc option. If not, some part of the cluster can be doubly
> revoked.
>
> Signed-off-by: Daeho Jeong <[email protected]>

Thanks, applied.

- Ted