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ocfs2: Find proper end cpos for a leaf refcount block.
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ocfs2 refcount tree is stored as an extent tree while
the leaf ocfs2_refcount_rec points to a refcount block.

The following step can trip a kernel panic.
mkfs.ocfs2 -b 512 -C 1M --fs-features=refcount $DEVICE
mount -t ocfs2 $DEVICE $MNT_DIR
FILE_NAME=$RANDOM
FILE_NAME_1=$RANDOM
FILE_REF="${FILE_NAME}_ref"
FILE_REF_1="${FILE_NAME}_ref_1"
for((i=0;i<305;i++))
do
# /mnt/1048576 is a file with 1048576 sizes.
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME_1
done
for((i=0;i<3;i++))
do
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME
done

for((i=0;i<2;i++))
do
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME_1
done

cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME

for((i=0;i<11;i++))
do
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME
cat /mnt/1048576 >> $MNT_DIR/$FILE_NAME_1
done
reflink $MNT_DIR/$FILE_NAME $MNT_DIR/$FILE_REF
# write_f is a program which will write some bytes to a file at offset.
# write_f -f file_name -l offset -w write_bytes.
./write_f -f $MNT_DIR/$FILE_REF -l $[310*1048576] -w 4096
./write_f -f $MNT_DIR/$FILE_REF -l $[306*1048576] -w 4096
./write_f -f $MNT_DIR/$FILE_REF -l $[311*1048576] -w 4096
./write_f -f $MNT_DIR/$FILE_NAME -l $[310*1048576] -w 4096
./write_f -f $MNT_DIR/$FILE_NAME -l $[311*1048576] -w 4096
reflink $MNT_DIR/$FILE_NAME $MNT_DIR/$FILE_REF_1
./write_f -f $MNT_DIR/$FILE_NAME -l $[311*1048576] -w 4096
#kernel panic here.

The reason is that if the ocfs2_extent_rec is the last record
in a leaf extent block, the old solution fails to find the
suitable end cpos. So this patch try to walk through the b-tree,
find the next sub root and get the c_pos the next sub-tree starts
from.

btw, I have runned tristan's test case against the patched kernel
for several days and this type of kernel panic never happens again.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
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Tao Ma authored and Joel Becker committed Dec 3, 2009
1 parent 56f3f55 commit 38a04e4
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Showing 3 changed files with 119 additions and 13 deletions.
10 changes: 5 additions & 5 deletions fs/ocfs2/alloc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1765,9 +1765,9 @@ static void ocfs2_create_empty_extent(struct ocfs2_extent_list *el)
*
* The array index of the subtree root is passed back.
*/
static int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
struct ocfs2_path *left,
struct ocfs2_path *right)
int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
struct ocfs2_path *left,
struct ocfs2_path *right)
{
int i = 0;

Expand Down Expand Up @@ -2872,8 +2872,8 @@ static int ocfs2_rotate_subtree_left(handle_t *handle,
* This looks similar, but is subtly different to
* ocfs2_find_cpos_for_left_leaf().
*/
static int ocfs2_find_cpos_for_right_leaf(struct super_block *sb,
struct ocfs2_path *path, u32 *cpos)
int ocfs2_find_cpos_for_right_leaf(struct super_block *sb,
struct ocfs2_path *path, u32 *cpos)
{
int i, j, ret = 0;
u64 blkno;
Expand Down
5 changes: 5 additions & 0 deletions fs/ocfs2/alloc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -317,4 +317,9 @@ int ocfs2_path_bh_journal_access(handle_t *handle,
int ocfs2_journal_access_path(struct ocfs2_caching_info *ci,
handle_t *handle,
struct ocfs2_path *path);
int ocfs2_find_cpos_for_right_leaf(struct super_block *sb,
struct ocfs2_path *path, u32 *cpos);
int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
struct ocfs2_path *left,
struct ocfs2_path *right);
#endif /* OCFS2_ALLOC_H */
117 changes: 109 additions & 8 deletions fs/ocfs2/refcounttree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -968,6 +968,103 @@ int ocfs2_try_remove_refcount_tree(struct inode *inode,
return 0;
}

/*
* Find the end range for a leaf refcount block indicated by
* el->l_recs[index].e_blkno.
*/
static int ocfs2_get_refcount_cpos_end(struct ocfs2_caching_info *ci,
struct buffer_head *ref_root_bh,
struct ocfs2_extent_block *eb,
struct ocfs2_extent_list *el,
int index, u32 *cpos_end)
{
int ret, i, subtree_root;
u32 cpos;
u64 blkno;
struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
struct ocfs2_path *left_path = NULL, *right_path = NULL;
struct ocfs2_extent_tree et;
struct ocfs2_extent_list *tmp_el;

if (index < le16_to_cpu(el->l_next_free_rec) - 1) {
/*
* We have a extent rec after index, so just use the e_cpos
* of the next extent rec.
*/
*cpos_end = le32_to_cpu(el->l_recs[index+1].e_cpos);
return 0;
}

if (!eb || (eb && !eb->h_next_leaf_blk)) {
/*
* We are the last extent rec, so any high cpos should
* be stored in this leaf refcount block.
*/
*cpos_end = UINT_MAX;
return 0;
}

/*
* If the extent block isn't the last one, we have to find
* the subtree root between this extent block and the next
* leaf extent block and get the corresponding e_cpos from
* the subroot. Otherwise we may corrupt the b-tree.
*/
ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);

left_path = ocfs2_new_path_from_et(&et);
if (!left_path) {
ret = -ENOMEM;
mlog_errno(ret);
goto out;
}

cpos = le32_to_cpu(eb->h_list.l_recs[index].e_cpos);
ret = ocfs2_find_path(ci, left_path, cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

right_path = ocfs2_new_path_from_path(left_path);
if (!right_path) {
ret = -ENOMEM;
mlog_errno(ret);
goto out;
}

ret = ocfs2_find_cpos_for_right_leaf(sb, left_path, &cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

ret = ocfs2_find_path(ci, right_path, cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

subtree_root = ocfs2_find_subtree_root(&et, left_path,
right_path);

tmp_el = left_path->p_node[subtree_root].el;
blkno = left_path->p_node[subtree_root+1].bh->b_blocknr;
for (i = 0; i < le32_to_cpu(tmp_el->l_next_free_rec); i++) {
if (le64_to_cpu(tmp_el->l_recs[i].e_blkno) == blkno) {
*cpos_end = le32_to_cpu(tmp_el->l_recs[i+1].e_cpos);
break;
}
}

BUG_ON(i == le32_to_cpu(tmp_el->l_next_free_rec));

out:
ocfs2_free_path(left_path);
ocfs2_free_path(right_path);
return ret;
}

/*
* Given a cpos and len, try to find the refcount record which contains cpos.
* 1. If cpos can be found in one refcount record, return the record.
Expand All @@ -983,10 +1080,10 @@ static int ocfs2_get_refcount_rec(struct ocfs2_caching_info *ci,
struct buffer_head **ret_bh)
{
int ret = 0, i, found;
u32 low_cpos;
u32 low_cpos, uninitialized_var(cpos_end);
struct ocfs2_extent_list *el;
struct ocfs2_extent_rec *tmp, *rec = NULL;
struct ocfs2_extent_block *eb;
struct ocfs2_extent_rec *rec = NULL;
struct ocfs2_extent_block *eb = NULL;
struct buffer_head *eb_bh = NULL, *ref_leaf_bh = NULL;
struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
struct ocfs2_refcount_block *rb =
Expand Down Expand Up @@ -1034,12 +1131,16 @@ static int ocfs2_get_refcount_rec(struct ocfs2_caching_info *ci,
}
}

/* adjust len when we have ocfs2_extent_rec after it. */
if (found && i < le16_to_cpu(el->l_next_free_rec) - 1) {
tmp = &el->l_recs[i+1];
if (found) {
ret = ocfs2_get_refcount_cpos_end(ci, ref_root_bh,
eb, el, i, &cpos_end);
if (ret) {
mlog_errno(ret);
goto out;
}

if (le32_to_cpu(tmp->e_cpos) < cpos + len)
len = le32_to_cpu(tmp->e_cpos) - cpos;
if (cpos_end < low_cpos + len)
len = cpos_end - low_cpos;
}

ret = ocfs2_read_refcount_block(ci, le64_to_cpu(rec->e_blkno),
Expand Down

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