ocfs2_defrag_extent may fall into deadlock.
ocfs2_ioctl_move_extents
ocfs2_ioctl_move_extents
ocfs2_move_extents
ocfs2_defrag_extent
ocfs2_lock_allocators_move_extents
ocfs2_reserve_clusters
inode_lock GLOBAL_BITMAP_SYSTEM_INODE
__ocfs2_flush_truncate_log
inode_lock GLOBAL_BITMAP_SYSTEM_INODE
As backtrace shows above, ocfs2_reserve_clusters() will call inode_lock
against the global bitmap if local allocator has not sufficient cluters.
Once global bitmap could meet the demand, ocfs2_reserve_cluster will
return success with global bitmap locked.
After ocfs2_reserve_cluster(), if truncate log is full,
__ocfs2_flush_truncate_log() will definitely fall into deadlock because it
needs to inode_lock global bitmap, which has already been locked.
To fix this bug, we could remove from ocfs2_lock_allocators_move_extents()
the code which intends to lock global allocator, and put the removed code
after __ocfs2_flush_truncate_log().
ocfs2_lock_allocators_move_extents() is referred by 2 places, one is here,
the other does not need the data allocator context, which means this patch
does not affect the caller so far.
Change log:
1. Correct the function comment.
2. Remove unused argument from ocfs2_lock_meta_allocator_move_extents.
Signed-off-by: Larry Chen <[email protected]>
---
fs/ocfs2/move_extents.c | 47 ++++++++++++++++++++++++++---------------------
1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
index 7eb3b0a6347e..f55f82ca3425 100644
--- a/fs/ocfs2/move_extents.c
+++ b/fs/ocfs2/move_extents.c
@@ -156,18 +156,14 @@ static int __ocfs2_move_extent(handle_t *handle,
}
/*
- * lock allocators, and reserving appropriate number of bits for
- * meta blocks and data clusters.
- *
- * in some cases, we don't need to reserve clusters, just let data_ac
- * be NULL.
+ * lock allocator, and reserve appropriate number of bits for
+ * meta blocks.
*/
-static int ocfs2_lock_allocators_move_extents(struct inode *inode,
+static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
struct ocfs2_extent_tree *et,
u32 clusters_to_move,
u32 extents_to_split,
struct ocfs2_alloc_context **meta_ac,
- struct ocfs2_alloc_context **data_ac,
int extra_blocks,
int *credits)
{
@@ -192,13 +188,6 @@ static int ocfs2_lock_allocators_move_extents(struct inode *inode,
goto out;
}
- if (data_ac) {
- ret = ocfs2_reserve_clusters(osb, clusters_to_move, data_ac);
- if (ret) {
- mlog_errno(ret);
- goto out;
- }
- }
*credits += ocfs2_calc_extend_credits(osb->sb, et->et_root_el);
@@ -257,10 +246,10 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
}
}
- ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
- &context->meta_ac,
- &context->data_ac,
- extra_blocks, &credits);
+ ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+ *len, 1,
+ &context->meta_ac,
+ extra_blocks, &credits);
if (ret) {
mlog_errno(ret);
goto out;
@@ -283,6 +272,21 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
}
}
+ /*
+ * Make sure ocfs2_reserve_cluster is called after
+ * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
+ *
+ * If ocfs2_reserve_cluster is called
+ * before __ocfs2_flush_truncate_log, dead lock on global bitmap
+ * may happen.
+ *
+ */
+ ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac);
+ if (ret) {
+ mlog_errno(ret);
+ goto out_unlock_mutex;
+ }
+
handle = ocfs2_start_trans(osb, credits);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
@@ -600,9 +604,10 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context,
}
}
- ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
- &context->meta_ac,
- NULL, extra_blocks, &credits);
+ ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+ len, 1,
+ &context->meta_ac,
+ extra_blocks, &credits);
if (ret) {
mlog_errno(ret);
goto out;
--
2.16.4
Hi Larry,
On 18/11/1 15:14, Larry Chen wrote:
> ocfs2_defrag_extent may fall into deadlock.
>
> ocfs2_ioctl_move_extents
> ocfs2_ioctl_move_extents
> ocfs2_move_extents
> ocfs2_defrag_extent
> ocfs2_lock_allocators_move_extents
>
> ocfs2_reserve_clusters
> inode_lock GLOBAL_BITMAP_SYSTEM_INODE
>
> __ocfs2_flush_truncate_log
> inode_lock GLOBAL_BITMAP_SYSTEM_INODE
>
> As backtrace shows above, ocfs2_reserve_clusters() will call inode_lock
> against the global bitmap if local allocator has not sufficient cluters.
> Once global bitmap could meet the demand, ocfs2_reserve_cluster will
> return success with global bitmap locked.
>
> After ocfs2_reserve_cluster(), if truncate log is full,
> __ocfs2_flush_truncate_log() will definitely fall into deadlock because it
> needs to inode_lock global bitmap, which has already been locked.
>
> To fix this bug, we could remove from ocfs2_lock_allocators_move_extents()
> the code which intends to lock global allocator, and put the removed code
> after __ocfs2_flush_truncate_log().
>
> ocfs2_lock_allocators_move_extents() is referred by 2 places, one is here,
> the other does not need the data allocator context, which means this patch
> does not affect the caller so far.
>
> Change log:
> 1. Correct the function comment.
> 2. Remove unused argument from ocfs2_lock_meta_allocator_move_extents.
>
> Signed-off-by: Larry Chen <[email protected]>
> ---
> fs/ocfs2/move_extents.c | 47 ++++++++++++++++++++++++++---------------------
> 1 file changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
> index 7eb3b0a6347e..f55f82ca3425 100644
> --- a/fs/ocfs2/move_extents.c
> +++ b/fs/ocfs2/move_extents.c
> @@ -156,18 +156,14 @@ static int __ocfs2_move_extent(handle_t *handle,
> }
>
> /*
> - * lock allocators, and reserving appropriate number of bits for
> - * meta blocks and data clusters.
> - *
> - * in some cases, we don't need to reserve clusters, just let data_ac
> - * be NULL.
> + * lock allocator, and reserve appropriate number of bits for
> + * meta blocks.
> */
> -static int ocfs2_lock_allocators_move_extents(struct inode *inode,
> +static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
> struct ocfs2_extent_tree *et,
> u32 clusters_to_move,
IMO, here clusters_to_move is only for data_ac, since we change this
function to only handle meta_ac, I'm afraid clusters_to_move related
logic has to been changed correspondingly.
Thanks,
Joseph
> u32 extents_to_split,
> struct ocfs2_alloc_context **meta_ac,
> - struct ocfs2_alloc_context **data_ac,
> int extra_blocks,
> int *credits)
> {
> @@ -192,13 +188,6 @@ static int ocfs2_lock_allocators_move_extents(struct inode *inode,
> goto out;
> }
>
> - if (data_ac) {
> - ret = ocfs2_reserve_clusters(osb, clusters_to_move, data_ac);
> - if (ret) {
> - mlog_errno(ret);
> - goto out;
> - }
> - }
>
> *credits += ocfs2_calc_extend_credits(osb->sb, et->et_root_el);
>
> @@ -257,10 +246,10 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> - ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
> - &context->meta_ac,
> - &context->data_ac,
> - extra_blocks, &credits);
> + ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
> + *len, 1,
> + &context->meta_ac,
> + extra_blocks, &credits);
> if (ret) {
> mlog_errno(ret);
> goto out;
> @@ -283,6 +272,21 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> + /*
> + * Make sure ocfs2_reserve_cluster is called after
> + * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
> + *
> + * If ocfs2_reserve_cluster is called
> + * before __ocfs2_flush_truncate_log, dead lock on global bitmap
> + * may happen.
> + *
> + */
> + ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac);
> + if (ret) {
> + mlog_errno(ret);
> + goto out_unlock_mutex;
> + }
> +
> handle = ocfs2_start_trans(osb, credits);
> if (IS_ERR(handle)) {
> ret = PTR_ERR(handle);
> @@ -600,9 +604,10 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> - ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
> - &context->meta_ac,
> - NULL, extra_blocks, &credits);
> + ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
> + len, 1,
> + &context->meta_ac,
> + extra_blocks, &credits);
> if (ret) {
> mlog_errno(ret);
> goto out;
>
Hi Larry,
The change looks good to me.
On 2018/11/1 15:14, Larry Chen wrote:
> ocfs2_defrag_extent may fall into deadlock.
>
> ocfs2_ioctl_move_extents
> ocfs2_ioctl_move_extents
> ocfs2_move_extents
> ocfs2_defrag_extent
> ocfs2_lock_allocators_move_extents
>
> ocfs2_reserve_clusters
> inode_lock GLOBAL_BITMAP_SYSTEM_INODE
>
> __ocfs2_flush_truncate_log
> inode_lock GLOBAL_BITMAP_SYSTEM_INODE
>
> As backtrace shows above, ocfs2_reserve_clusters() will call inode_lock
> against the global bitmap if local allocator has not sufficient cluters.
> Once global bitmap could meet the demand, ocfs2_reserve_cluster will
> return success with global bitmap locked.
>
> After ocfs2_reserve_cluster(), if truncate log is full,
> __ocfs2_flush_truncate_log() will definitely fall into deadlock because it
> needs to inode_lock global bitmap, which has already been locked.
>
> To fix this bug, we could remove from ocfs2_lock_allocators_move_extents()
> the code which intends to lock global allocator, and put the removed code
> after __ocfs2_flush_truncate_log().
>
> ocfs2_lock_allocators_move_extents() is referred by 2 places, one is here,
> the other does not need the data allocator context, which means this patch
> does not affect the caller so far.
>
> Change log:
> 1. Correct the function comment.
> 2. Remove unused argument from ocfs2_lock_meta_allocator_move_extents.
>
> Signed-off-by: Larry Chen <[email protected]>
Reviewed-by: Changwei Ge <[email protected]>
> ---
> fs/ocfs2/move_extents.c | 47 ++++++++++++++++++++++++++---------------------
> 1 file changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
> index 7eb3b0a6347e..f55f82ca3425 100644
> --- a/fs/ocfs2/move_extents.c
> +++ b/fs/ocfs2/move_extents.c
> @@ -156,18 +156,14 @@ static int __ocfs2_move_extent(handle_t *handle,
> }
>
> /*
> - * lock allocators, and reserving appropriate number of bits for
> - * meta blocks and data clusters.
> - *
> - * in some cases, we don't need to reserve clusters, just let data_ac
> - * be NULL.
> + * lock allocator, and reserve appropriate number of bits for
> + * meta blocks.
> */
> -static int ocfs2_lock_allocators_move_extents(struct inode *inode,
> +static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
> struct ocfs2_extent_tree *et,
> u32 clusters_to_move,
> u32 extents_to_split,
> struct ocfs2_alloc_context **meta_ac,
> - struct ocfs2_alloc_context **data_ac,
> int extra_blocks,
> int *credits)
> {
> @@ -192,13 +188,6 @@ static int ocfs2_lock_allocators_move_extents(struct inode *inode,
> goto out;
> }
>
> - if (data_ac) {
> - ret = ocfs2_reserve_clusters(osb, clusters_to_move, data_ac);
> - if (ret) {
> - mlog_errno(ret);
> - goto out;
> - }
> - }
>
> *credits += ocfs2_calc_extend_credits(osb->sb, et->et_root_el);
>
> @@ -257,10 +246,10 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> - ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
> - &context->meta_ac,
> - &context->data_ac,
> - extra_blocks, &credits);
> + ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
> + *len, 1,
> + &context->meta_ac,
> + extra_blocks, &credits);
> if (ret) {
> mlog_errno(ret);
> goto out;
> @@ -283,6 +272,21 @@ static int ocfs2_defrag_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> + /*
> + * Make sure ocfs2_reserve_cluster is called after
> + * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
> + *
> + * If ocfs2_reserve_cluster is called
> + * before __ocfs2_flush_truncate_log, dead lock on global bitmap
> + * may happen.
> + *
> + */
> + ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac);
> + if (ret) {
> + mlog_errno(ret);
> + goto out_unlock_mutex;
> + }
> +
> handle = ocfs2_start_trans(osb, credits);
> if (IS_ERR(handle)) {
> ret = PTR_ERR(handle);
> @@ -600,9 +604,10 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context,
> }
> }
>
> - ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
> - &context->meta_ac,
> - NULL, extra_blocks, &credits);
> + ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
> + len, 1,
> + &context->meta_ac,
> + extra_blocks, &credits);
> if (ret) {
> mlog_errno(ret);
> goto out;
>