* Re: [PATCH] Btrfs: skip commit transaction if we don't have enough pinned bytes
2017-06-02 18:14 ` Omar Sandoval
@ 2017-06-04 1:31 ` Holger Hoffstätte
2017-06-05 22:05 ` Liu Bo
2017-06-06 4:29 ` Liu Bo
2 siblings, 0 replies; 9+ messages in thread
From: Holger Hoffstätte @ 2017-06-04 1:31 UTC (permalink / raw)
To: Omar Sandoval, Liu Bo; +Cc: linux-btrfs
On 06/02/17 20:14, Omar Sandoval wrote:
> On Fri, May 19, 2017 at 11:39:15AM -0600, Liu Bo wrote:
>> We commit transaction in order to reclaim space from pinned bytes because
>> it could process delayed refs, and in may_commit_transaction(), we check
>> first if pinned bytes are enough for the required space, we then check if
>> that plus bytes reserved for delayed insert are enough for the required
>> space.
>>
>> This changes the code to the above logic.
>>
>> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
>> ---
>> fs/btrfs/extent-tree.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index e390451c72e6..bded1ddd1bb6 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -4837,7 +4837,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
>>
>> spin_lock(&delayed_rsv->lock);
>> if (percpu_counter_compare(&space_info->total_bytes_pinned,
>> - bytes - delayed_rsv->size) >= 0) {
>> + bytes - delayed_rsv->size) < 0) {
>> spin_unlock(&delayed_rsv->lock);
>> return -ENOSPC;
>> }
>
> I found this bug in my latest enospc investigation, too. However, the
> total_bytes_pinned counter is pretty broken. E.g., on my laptop:
>
> $ sync; grep -H '' /sys/fs/btrfs/*/allocation/*/total_bytes_pinned
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/data/total_bytes_pinned:48693501952
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/metadata/total_bytes_pinned:-258146304
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/system/total_bytes_pinned:0
>
> I have a patch to fix it that I haven't cleaned up yet, below. Without
> it, Bo's fix will probably cause early ENOSPCs. Dave, should we pull
> Bo's patch out of for-next? In any case, I'll get my fix sent out.
[..patch snipped..]
This made me curious since I also found the underflowed metadata counter
on my system. I tried to reproduce it after un/remount (to reset the counters)
and noticed that I could reliably cause the metadata underflow by defragging
a few large subvolumes, which apparently creates enough extent tree movement
that the counter quickly goes bananas. It took some backporting, but with your
patch applied I can defrag away and have so far not seen a single counter
underflow; all of data/metadata/system are always positive after writes and
then reliably drop to 0 after sync/commit. Nice!
Just thought you'd want to know.
Holger
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH] Btrfs: skip commit transaction if we don't have enough pinned bytes
2017-06-02 18:14 ` Omar Sandoval
2017-06-04 1:31 ` Holger Hoffstätte
@ 2017-06-05 22:05 ` Liu Bo
2017-06-06 4:29 ` Liu Bo
2 siblings, 0 replies; 9+ messages in thread
From: Liu Bo @ 2017-06-05 22:05 UTC (permalink / raw)
To: Omar Sandoval; +Cc: linux-btrfs
On Fri, Jun 02, 2017 at 11:14:13AM -0700, Omar Sandoval wrote:
> On Fri, May 19, 2017 at 11:39:15AM -0600, Liu Bo wrote:
> > We commit transaction in order to reclaim space from pinned bytes because
> > it could process delayed refs, and in may_commit_transaction(), we check
> > first if pinned bytes are enough for the required space, we then check if
> > that plus bytes reserved for delayed insert are enough for the required
> > space.
> >
> > This changes the code to the above logic.
> >
> > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > ---
> > fs/btrfs/extent-tree.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> > index e390451c72e6..bded1ddd1bb6 100644
> > --- a/fs/btrfs/extent-tree.c
> > +++ b/fs/btrfs/extent-tree.c
> > @@ -4837,7 +4837,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> >
> > spin_lock(&delayed_rsv->lock);
> > if (percpu_counter_compare(&space_info->total_bytes_pinned,
> > - bytes - delayed_rsv->size) >= 0) {
> > + bytes - delayed_rsv->size) < 0) {
> > spin_unlock(&delayed_rsv->lock);
> > return -ENOSPC;
> > }
>
> I found this bug in my latest enospc investigation, too. However, the
> total_bytes_pinned counter is pretty broken. E.g., on my laptop:
>
> $ sync; grep -H '' /sys/fs/btrfs/*/allocation/*/total_bytes_pinned
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/data/total_bytes_pinned:48693501952
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/metadata/total_bytes_pinned:-258146304
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/system/total_bytes_pinned:0
>
> I have a patch to fix it that I haven't cleaned up yet, below. Without
> it, Bo's fix will probably cause early ENOSPCs. Dave, should we pull
> Bo's patch out of for-next? In any case, I'll get my fix sent out.
>
While it does result in early ENOSPC, I don't think it's that fix's
problem, but because we don't precisely track this %pinned counter.
It has shown metadata's %total_bytes_pinned that is negative, have you
seen a negative counter for data?
The problem I observed is btrfs_free_tree_block(), which doesn't add
pinned bytes when it's not the last reference, while
__btrfs_free_extent() dec pinned bytes when it's not the last ref. (I
have made a simple reproducer.)
But for data, looks like we could over-add pinned bytes if a removed
ref got re-added later, I'll try to make a test for this case.
> diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
> index be70d90dfee5..93ffa898df6d 100644
> --- a/fs/btrfs/delayed-ref.c
> +++ b/fs/btrfs/delayed-ref.c
> @@ -470,7 +470,8 @@ add_delayed_ref_tail_merge(struct btrfs_trans_handle *trans,
> static noinline void
> update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs,
> struct btrfs_delayed_ref_node *existing,
> - struct btrfs_delayed_ref_node *update)
> + struct btrfs_delayed_ref_node *update,
> + int *old_ref_mod_ret)
The head ref doesn't seem related to the negative thing, we dec the
counter when running delayed refs, not head ref.
> {
> struct btrfs_delayed_ref_head *existing_ref;
> struct btrfs_delayed_ref_head *ref;
> @@ -523,6 +524,8 @@ update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs,
> * currently, for refs we just added we know we're a-ok.
> */
> old_ref_mod = existing_ref->total_ref_mod;
> + if (old_ref_mod_ret)
> + *old_ref_mod_ret = old_ref_mod;
> existing->ref_mod += update->ref_mod;
> existing_ref->total_ref_mod += update->ref_mod;
>
> @@ -550,7 +553,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> struct btrfs_delayed_ref_node *ref,
> struct btrfs_qgroup_extent_record *qrecord,
> u64 bytenr, u64 num_bytes, u64 ref_root, u64 reserved,
> - int action, int is_data, int *qrecord_inserted_ret)
> + int action, int is_data, int *qrecord_inserted_ret,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_ref_head *existing;
> struct btrfs_delayed_ref_head *head_ref = NULL;
> @@ -638,7 +642,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> if (existing) {
> WARN_ON(ref_root && reserved && existing->qgroup_ref_root
> && existing->qgroup_reserved);
> - update_existing_head_ref(delayed_refs, &existing->node, ref);
> + update_existing_head_ref(delayed_refs, &existing->node, ref,
> + old_ref_mod);
> /*
> * we've updated the existing ref, free the newly
> * allocated ref
> @@ -646,6 +651,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
> head_ref = existing;
> } else {
> + if (old_ref_mod)
> + *old_ref_mod = 0;
> if (is_data && count_mod < 0)
> delayed_refs->pending_csums += num_bytes;
> delayed_refs->num_heads++;
> @@ -655,6 +662,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> }
> if (qrecord_inserted_ret)
> *qrecord_inserted_ret = qrecord_inserted;
> + if (new_ref_mod)
> + *new_ref_mod = head_ref->total_ref_mod;
> return head_ref;
> }
>
> @@ -778,7 +787,8 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 ref_root, int level, int action,
> - struct btrfs_delayed_extent_op *extent_op)
> + struct btrfs_delayed_extent_op *extent_op,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_tree_ref *ref;
> struct btrfs_delayed_ref_head *head_ref;
> @@ -813,7 +823,8 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> */
> head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node, record,
> bytenr, num_bytes, 0, 0, action, 0,
> - &qrecord_inserted);
> + &qrecord_inserted, old_ref_mod,
> + new_ref_mod);
>
> add_delayed_tree_ref(fs_info, trans, head_ref, &ref->node, bytenr,
> num_bytes, parent, ref_root, level, action);
> @@ -838,7 +849,8 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> u64 parent, u64 ref_root,
> - u64 owner, u64 offset, u64 reserved, int action)
> + u64 owner, u64 offset, u64 reserved, int action,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_data_ref *ref;
> struct btrfs_delayed_ref_head *head_ref;
> @@ -878,7 +890,8 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> */
> head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node, record,
> bytenr, num_bytes, ref_root, reserved,
> - action, 1, &qrecord_inserted);
> + action, 1, &qrecord_inserted,
> + old_ref_mod, new_ref_mod);
>
> add_delayed_data_ref(fs_info, trans, head_ref, &ref->node, bytenr,
> num_bytes, parent, ref_root, owner, offset,
> @@ -909,7 +922,7 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
>
> add_delayed_ref_head(fs_info, trans, &head_ref->node, NULL, bytenr,
> num_bytes, 0, 0, BTRFS_UPDATE_DELAYED_HEAD,
> - extent_op->is_data, NULL);
> + extent_op->is_data, NULL, NULL, NULL);
>
> spin_unlock(&delayed_refs->lock);
> return 0;
> diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
> index c0264ff01b53..ce88e4ac5276 100644
> --- a/fs/btrfs/delayed-ref.h
> +++ b/fs/btrfs/delayed-ref.h
> @@ -247,12 +247,14 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 ref_root, int level, int action,
> - struct btrfs_delayed_extent_op *extent_op);
> + struct btrfs_delayed_extent_op *extent_op,
> + int *old_ref_mod, int *new_ref_mod);
> int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> u64 parent, u64 ref_root,
> - u64 owner, u64 offset, u64 reserved, int action);
> + u64 owner, u64 offset, u64 reserved, int action,
> + int *old_ref_mod, int *new_ref_mod);
> int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e390451c72e6..78cde661997b 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -107,6 +107,8 @@ static void space_info_add_new_bytes(struct btrfs_fs_info *fs_info,
> static void space_info_add_old_bytes(struct btrfs_fs_info *fs_info,
> struct btrfs_space_info *space_info,
> u64 num_bytes);
> +static void add_pinned_bytes(struct btrfs_fs_info *fs_info, s64 num_bytes,
> + u64 owner, u64 root_objectid);
>
> static noinline int
> block_group_cache_done(struct btrfs_block_group_cache *cache)
> @@ -2092,6 +2094,7 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 root_objectid, u64 owner, u64 offset)
> {
> + int old_ref_mod, new_ref_mod;
> int ret;
>
> BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID &&
> @@ -2099,15 +2102,21 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>
> if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> ret = btrfs_add_delayed_tree_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, (int)owner,
> - BTRFS_ADD_DELAYED_REF, NULL);
> + num_bytes, parent,
> + root_objectid, (int)owner,
> + BTRFS_ADD_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> } else {
> ret = btrfs_add_delayed_data_ref(fs_info, trans, bytenr,
> - num_bytes, parent, root_objectid,
> - owner, offset, 0,
> - BTRFS_ADD_DELAYED_REF);
> + num_bytes, parent,
> + root_objectid, owner, offset,
> + 0, BTRFS_ADD_DELAYED_REF,
> + &old_ref_mod, &new_ref_mod);
> }
> +
> + if (ret == 0 && old_ref_mod < 0 && new_ref_mod >= 0)
> + add_pinned_bytes(fs_info, -num_bytes, owner, root_objectid);
> +
> return ret;
> }
>
> @@ -2401,6 +2410,7 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
>
> if (btrfs_delayed_ref_is_head(node)) {
> struct btrfs_delayed_ref_head *head;
> +
> /*
> * we've hit the end of the chain and we were supposed
> * to insert this extent into the tree. But, it got
> @@ -2411,6 +2421,17 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
> head = btrfs_delayed_node_to_head(node);
> trace_run_delayed_ref_head(fs_info, node, head, node->action);
>
> + if (head->total_ref_mod < 0) {
> + struct btrfs_block_group_cache *cache;
> +
> + cache = btrfs_lookup_block_group(fs_info, node->bytenr);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned,
> + -node->num_bytes);
> + BUG_ON(!cache); /* Logic error */
> +
> + btrfs_put_block_group(cache);
> + }
> +
> if (insert_reserved) {
> btrfs_pin_extent(fs_info, node->bytenr,
> node->num_bytes, 1);
> @@ -6247,6 +6268,8 @@ static int update_block_group(struct btrfs_trans_handle *trans,
> trace_btrfs_space_reservation(info, "pinned",
> cache->space_info->flags,
> num_bytes, 1);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned,
> + num_bytes);
> set_extent_dirty(info->pinned_extents,
> bytenr, bytenr + num_bytes - 1,
> GFP_NOFS | __GFP_NOFAIL);
> @@ -6323,6 +6346,7 @@ static int pin_down_extent(struct btrfs_fs_info *fs_info,
>
> trace_btrfs_space_reservation(fs_info, "pinned",
> cache->space_info->flags, num_bytes, 1);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned, num_bytes);
> set_extent_dirty(fs_info->pinned_extents, bytenr,
> bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
> return 0;
> @@ -6793,7 +6817,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
> return 0;
> }
>
> -static void add_pinned_bytes(struct btrfs_fs_info *fs_info, u64 num_bytes,
> +static void add_pinned_bytes(struct btrfs_fs_info *fs_info, s64 num_bytes,
> u64 owner, u64 root_objectid)
> {
> struct btrfs_space_info *space_info;
> @@ -7036,8 +7060,6 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
> goto out;
> }
> }
> - add_pinned_bytes(info, -num_bytes, owner_objectid,
> - root_objectid);
> } else {
> if (found_extent) {
> BUG_ON(is_data && refs_to_drop !=
> @@ -7169,19 +7191,19 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> int ret;
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> - ret = btrfs_add_delayed_tree_ref(fs_info, trans,
> - buf->start, buf->len,
> - parent,
> + int old_ref_mod, new_ref_mod;
> +
> + ret = btrfs_add_delayed_tree_ref(fs_info, trans, buf->start,
> + buf->len, parent,
> root->root_key.objectid,
> btrfs_header_level(buf),
> - BTRFS_DROP_DELAYED_REF, NULL);
> + BTRFS_DROP_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> BUG_ON(ret); /* -ENOMEM */
> + pin = old_ref_mod >= 0 && new_ref_mod < 0;
> }
>
> - if (!last_ref)
> - return;
> -
> - if (btrfs_header_generation(buf) == trans->transid) {
> + if (last_ref && btrfs_header_generation(buf) == trans->transid) {
> struct btrfs_block_group_cache *cache;
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> @@ -7190,6 +7212,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> goto out;
> }
>
> + pin = 0;
> cache = btrfs_lookup_block_group(fs_info, buf->start);
>
> if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
> @@ -7205,18 +7228,19 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> btrfs_free_reserved_bytes(cache, buf->len, 0);
> btrfs_put_block_group(cache);
> trace_btrfs_reserved_extent_free(fs_info, buf->start, buf->len);
> - pin = 0;
> }
> out:
> if (pin)
> add_pinned_bytes(fs_info, buf->len, btrfs_header_level(buf),
> root->root_key.objectid);
>
> - /*
> - * Deleting the buffer, clear the corrupt flag since it doesn't matter
> - * anymore.
> - */
> - clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + if (last_ref) {
> + /*
> + * Deleting the buffer, clear the corrupt flag since it doesn't matter
> + * anymore.
> + */
> + clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + }
Only appling the above 3 chunks of diff can fix the negative counter
found by my reproducer.
thanks,
-liubo
> }
>
> /* Can return -ENOMEM */
> @@ -7225,12 +7249,12 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent, u64 root_objectid,
> u64 owner, u64 offset)
> {
> + int old_ref_mod, new_ref_mod;
> int ret;
>
> if (btrfs_is_testing(fs_info))
> return 0;
>
> - add_pinned_bytes(fs_info, num_bytes, owner, root_objectid);
>
> /*
> * tree log blocks never actually go into the extent allocation
> @@ -7240,19 +7264,25 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans,
> WARN_ON(owner >= BTRFS_FIRST_FREE_OBJECTID);
> /* unlocks the pinned mutex */
> btrfs_pin_extent(fs_info, bytenr, num_bytes, 1);
> + old_ref_mod = new_ref_mod = 0;
> ret = 0;
> } else if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> ret = btrfs_add_delayed_tree_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, (int)owner,
> - BTRFS_DROP_DELAYED_REF, NULL);
> + p num_bytes, parent,
> + root_objectid, (int)owner,
> + BTRFS_DROP_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> } else {
> ret = btrfs_add_delayed_data_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, owner,
> - offset, 0,
> - BTRFS_DROP_DELAYED_REF);
> + num_bytes, parent,
> + root_objectid, owner, offset,
> + 0, BTRFS_DROP_DELAYED_REF,
> + &old_ref_mod, &new_ref_mod);
> }
> +
> + if (ret == 0 && old_ref_mod >= 0 && new_ref_mod < 0)
> + add_pinned_bytes(fs_info, num_bytes, owner, root_objectid);
> +
> return ret;
> }
>
> @@ -8199,9 +8229,9 @@ int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
> BUG_ON(root_objectid == BTRFS_TREE_LOG_OBJECTID);
>
> ret = btrfs_add_delayed_data_ref(fs_info, trans, ins->objectid,
> - ins->offset, 0,
> - root_objectid, owner, offset,
> - ram_bytes, BTRFS_ADD_DELAYED_EXTENT);
> + ins->offset, 0, root_objectid, owner,
> + offset, ram_bytes,
> + BTRFS_ADD_DELAYED_EXTENT, NULL, NULL);
> return ret;
> }
>
> @@ -8421,11 +8451,11 @@ struct extent_buffer *btrfs_alloc_tree_block(struct btrfs_trans_handle *trans,
> extent_op->is_data = false;
> extent_op->level = level;
>
> - ret = btrfs_add_delayed_tree_ref(fs_info, trans,
> - ins.objectid, ins.offset,
> - parent, root_objectid, level,
> + ret = btrfs_add_delayed_tree_ref(fs_info, trans, ins.objectid,
> + ins.offset, parent,
> + root_objectid, level,
> BTRFS_ADD_DELAYED_EXTENT,
> - extent_op);
> + extent_op, NULL, NULL);
> if (ret)
> goto out_free_delayed;
> }
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH] Btrfs: skip commit transaction if we don't have enough pinned bytes
2017-06-02 18:14 ` Omar Sandoval
2017-06-04 1:31 ` Holger Hoffstätte
2017-06-05 22:05 ` Liu Bo
@ 2017-06-06 4:29 ` Liu Bo
2017-06-06 23:47 ` Omar Sandoval
2 siblings, 1 reply; 9+ messages in thread
From: Liu Bo @ 2017-06-06 4:29 UTC (permalink / raw)
To: Omar Sandoval; +Cc: linux-btrfs
On Fri, Jun 02, 2017 at 11:14:13AM -0700, Omar Sandoval wrote:
> On Fri, May 19, 2017 at 11:39:15AM -0600, Liu Bo wrote:
> > We commit transaction in order to reclaim space from pinned bytes because
> > it could process delayed refs, and in may_commit_transaction(), we check
> > first if pinned bytes are enough for the required space, we then check if
> > that plus bytes reserved for delayed insert are enough for the required
> > space.
> >
> > This changes the code to the above logic.
> >
> > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > ---
> > fs/btrfs/extent-tree.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> > index e390451c72e6..bded1ddd1bb6 100644
> > --- a/fs/btrfs/extent-tree.c
> > +++ b/fs/btrfs/extent-tree.c
> > @@ -4837,7 +4837,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> >
> > spin_lock(&delayed_rsv->lock);
> > if (percpu_counter_compare(&space_info->total_bytes_pinned,
> > - bytes - delayed_rsv->size) >= 0) {
> > + bytes - delayed_rsv->size) < 0) {
> > spin_unlock(&delayed_rsv->lock);
> > return -ENOSPC;
> > }
>
> I found this bug in my latest enospc investigation, too. However, the
> total_bytes_pinned counter is pretty broken. E.g., on my laptop:
>
> $ sync; grep -H '' /sys/fs/btrfs/*/allocation/*/total_bytes_pinned
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/data/total_bytes_pinned:48693501952
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/metadata/total_bytes_pinned:-258146304
> /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/system/total_bytes_pinned:0
>
> I have a patch to fix it that I haven't cleaned up yet, below. Without
> it, Bo's fix will probably cause early ENOSPCs. Dave, should we pull
> Bo's patch out of for-next? In any case, I'll get my fix sent out.
>
When data delayed refs are not merged, __btrfs_free_extent() will dec
the pinned as expected, but when they got merged, %pinned bytes only
got inc'd but not dec'd because the delayed ref has been deleted due
to ref_count == 0.
This doesn't happen to tree block ref since tree block ref doesn't
have more than one ref, so ref_mod is either 1 or -1, and tree block
ref gets removed via btrfs_free_tree_block(), which also needs to be
changed.
Based on that, I think we can solve the problem by touching
btrfs_free_tree_block() and data delayed ref instead of head ref.
thanks,
-liubo
> diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
> index be70d90dfee5..93ffa898df6d 100644
> --- a/fs/btrfs/delayed-ref.c
> +++ b/fs/btrfs/delayed-ref.c
> @@ -470,7 +470,8 @@ add_delayed_ref_tail_merge(struct btrfs_trans_handle *trans,
> static noinline void
> update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs,
> struct btrfs_delayed_ref_node *existing,
> - struct btrfs_delayed_ref_node *update)
> + struct btrfs_delayed_ref_node *update,
> + int *old_ref_mod_ret)
> {
> struct btrfs_delayed_ref_head *existing_ref;
> struct btrfs_delayed_ref_head *ref;
> @@ -523,6 +524,8 @@ update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs,
> * currently, for refs we just added we know we're a-ok.
> */
> old_ref_mod = existing_ref->total_ref_mod;
> + if (old_ref_mod_ret)
> + *old_ref_mod_ret = old_ref_mod;
> existing->ref_mod += update->ref_mod;
> existing_ref->total_ref_mod += update->ref_mod;
>
> @@ -550,7 +553,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> struct btrfs_delayed_ref_node *ref,
> struct btrfs_qgroup_extent_record *qrecord,
> u64 bytenr, u64 num_bytes, u64 ref_root, u64 reserved,
> - int action, int is_data, int *qrecord_inserted_ret)
> + int action, int is_data, int *qrecord_inserted_ret,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_ref_head *existing;
> struct btrfs_delayed_ref_head *head_ref = NULL;
> @@ -638,7 +642,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> if (existing) {
> WARN_ON(ref_root && reserved && existing->qgroup_ref_root
> && existing->qgroup_reserved);
> - update_existing_head_ref(delayed_refs, &existing->node, ref);
> + update_existing_head_ref(delayed_refs, &existing->node, ref,
> + old_ref_mod);
> /*
> * we've updated the existing ref, free the newly
> * allocated ref
> @@ -646,6 +651,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
> head_ref = existing;
> } else {
> + if (old_ref_mod)
> + *old_ref_mod = 0;
> if (is_data && count_mod < 0)
> delayed_refs->pending_csums += num_bytes;
> delayed_refs->num_heads++;
> @@ -655,6 +662,8 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
> }
> if (qrecord_inserted_ret)
> *qrecord_inserted_ret = qrecord_inserted;
> + if (new_ref_mod)
> + *new_ref_mod = head_ref->total_ref_mod;
> return head_ref;
> }
>
> @@ -778,7 +787,8 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 ref_root, int level, int action,
> - struct btrfs_delayed_extent_op *extent_op)
> + struct btrfs_delayed_extent_op *extent_op,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_tree_ref *ref;
> struct btrfs_delayed_ref_head *head_ref;
> @@ -813,7 +823,8 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> */
> head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node, record,
> bytenr, num_bytes, 0, 0, action, 0,
> - &qrecord_inserted);
> + &qrecord_inserted, old_ref_mod,
> + new_ref_mod);
>
> add_delayed_tree_ref(fs_info, trans, head_ref, &ref->node, bytenr,
> num_bytes, parent, ref_root, level, action);
> @@ -838,7 +849,8 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> u64 parent, u64 ref_root,
> - u64 owner, u64 offset, u64 reserved, int action)
> + u64 owner, u64 offset, u64 reserved, int action,
> + int *old_ref_mod, int *new_ref_mod)
> {
> struct btrfs_delayed_data_ref *ref;
> struct btrfs_delayed_ref_head *head_ref;
> @@ -878,7 +890,8 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> */
> head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node, record,
> bytenr, num_bytes, ref_root, reserved,
> - action, 1, &qrecord_inserted);
> + action, 1, &qrecord_inserted,
> + old_ref_mod, new_ref_mod);
>
> add_delayed_data_ref(fs_info, trans, head_ref, &ref->node, bytenr,
> num_bytes, parent, ref_root, owner, offset,
> @@ -909,7 +922,7 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
>
> add_delayed_ref_head(fs_info, trans, &head_ref->node, NULL, bytenr,
> num_bytes, 0, 0, BTRFS_UPDATE_DELAYED_HEAD,
> - extent_op->is_data, NULL);
> + extent_op->is_data, NULL, NULL, NULL);
>
> spin_unlock(&delayed_refs->lock);
> return 0;
> diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
> index c0264ff01b53..ce88e4ac5276 100644
> --- a/fs/btrfs/delayed-ref.h
> +++ b/fs/btrfs/delayed-ref.h
> @@ -247,12 +247,14 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 ref_root, int level, int action,
> - struct btrfs_delayed_extent_op *extent_op);
> + struct btrfs_delayed_extent_op *extent_op,
> + int *old_ref_mod, int *new_ref_mod);
> int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> u64 parent, u64 ref_root,
> - u64 owner, u64 offset, u64 reserved, int action);
> + u64 owner, u64 offset, u64 reserved, int action,
> + int *old_ref_mod, int *new_ref_mod);
> int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes,
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e390451c72e6..78cde661997b 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -107,6 +107,8 @@ static void space_info_add_new_bytes(struct btrfs_fs_info *fs_info,
> static void space_info_add_old_bytes(struct btrfs_fs_info *fs_info,
> struct btrfs_space_info *space_info,
> u64 num_bytes);
> +static void add_pinned_bytes(struct btrfs_fs_info *fs_info, s64 num_bytes,
> + u64 owner, u64 root_objectid);
>
> static noinline int
> block_group_cache_done(struct btrfs_block_group_cache *cache)
> @@ -2092,6 +2094,7 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent,
> u64 root_objectid, u64 owner, u64 offset)
> {
> + int old_ref_mod, new_ref_mod;
> int ret;
>
> BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID &&
> @@ -2099,15 +2102,21 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>
> if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> ret = btrfs_add_delayed_tree_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, (int)owner,
> - BTRFS_ADD_DELAYED_REF, NULL);
> + num_bytes, parent,
> + root_objectid, (int)owner,
> + BTRFS_ADD_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> } else {
> ret = btrfs_add_delayed_data_ref(fs_info, trans, bytenr,
> - num_bytes, parent, root_objectid,
> - owner, offset, 0,
> - BTRFS_ADD_DELAYED_REF);
> + num_bytes, parent,
> + root_objectid, owner, offset,
> + 0, BTRFS_ADD_DELAYED_REF,
> + &old_ref_mod, &new_ref_mod);
> }
> +
> + if (ret == 0 && old_ref_mod < 0 && new_ref_mod >= 0)
> + add_pinned_bytes(fs_info, -num_bytes, owner, root_objectid);
> +
> return ret;
> }
>
> @@ -2401,6 +2410,7 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
>
> if (btrfs_delayed_ref_is_head(node)) {
> struct btrfs_delayed_ref_head *head;
> +
> /*
> * we've hit the end of the chain and we were supposed
> * to insert this extent into the tree. But, it got
> @@ -2411,6 +2421,17 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
> head = btrfs_delayed_node_to_head(node);
> trace_run_delayed_ref_head(fs_info, node, head, node->action);
>
> + if (head->total_ref_mod < 0) {
> + struct btrfs_block_group_cache *cache;
> +
> + cache = btrfs_lookup_block_group(fs_info, node->bytenr);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned,
> + -node->num_bytes);
> + BUG_ON(!cache); /* Logic error */
> +
> + btrfs_put_block_group(cache);
> + }
> +
> if (insert_reserved) {
> btrfs_pin_extent(fs_info, node->bytenr,
> node->num_bytes, 1);
> @@ -6247,6 +6268,8 @@ static int update_block_group(struct btrfs_trans_handle *trans,
> trace_btrfs_space_reservation(info, "pinned",
> cache->space_info->flags,
> num_bytes, 1);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned,
> + num_bytes);
> set_extent_dirty(info->pinned_extents,
> bytenr, bytenr + num_bytes - 1,
> GFP_NOFS | __GFP_NOFAIL);
> @@ -6323,6 +6346,7 @@ static int pin_down_extent(struct btrfs_fs_info *fs_info,
>
> trace_btrfs_space_reservation(fs_info, "pinned",
> cache->space_info->flags, num_bytes, 1);
> + percpu_counter_add(&cache->space_info->total_bytes_pinned, num_bytes);
> set_extent_dirty(fs_info->pinned_extents, bytenr,
> bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
> return 0;
> @@ -6793,7 +6817,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
> return 0;
> }
>
> -static void add_pinned_bytes(struct btrfs_fs_info *fs_info, u64 num_bytes,
> +static void add_pinned_bytes(struct btrfs_fs_info *fs_info, s64 num_bytes,
> u64 owner, u64 root_objectid)
> {
> struct btrfs_space_info *space_info;
> @@ -7036,8 +7060,6 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
> goto out;
> }
> }
> - add_pinned_bytes(info, -num_bytes, owner_objectid,
> - root_objectid);
> } else {
> if (found_extent) {
> BUG_ON(is_data && refs_to_drop !=
> @@ -7169,19 +7191,19 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> int ret;
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> - ret = btrfs_add_delayed_tree_ref(fs_info, trans,
> - buf->start, buf->len,
> - parent,
> + int old_ref_mod, new_ref_mod;
> +
> + ret = btrfs_add_delayed_tree_ref(fs_info, trans, buf->start,
> + buf->len, parent,
> root->root_key.objectid,
> btrfs_header_level(buf),
> - BTRFS_DROP_DELAYED_REF, NULL);
> + BTRFS_DROP_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> BUG_ON(ret); /* -ENOMEM */
> + pin = old_ref_mod >= 0 && new_ref_mod < 0;
> }
>
> - if (!last_ref)
> - return;
> -
> - if (btrfs_header_generation(buf) == trans->transid) {
> + if (last_ref && btrfs_header_generation(buf) == trans->transid) {
> struct btrfs_block_group_cache *cache;
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> @@ -7190,6 +7212,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> goto out;
> }
>
> + pin = 0;
> cache = btrfs_lookup_block_group(fs_info, buf->start);
>
> if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
> @@ -7205,18 +7228,19 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
> btrfs_free_reserved_bytes(cache, buf->len, 0);
> btrfs_put_block_group(cache);
> trace_btrfs_reserved_extent_free(fs_info, buf->start, buf->len);
> - pin = 0;
> }
> out:
> if (pin)
> add_pinned_bytes(fs_info, buf->len, btrfs_header_level(buf),
> root->root_key.objectid);
>
> - /*
> - * Deleting the buffer, clear the corrupt flag since it doesn't matter
> - * anymore.
> - */
> - clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + if (last_ref) {
> + /*
> + * Deleting the buffer, clear the corrupt flag since it doesn't matter
> + * anymore.
> + */
> + clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + }
> }
>
> /* Can return -ENOMEM */
> @@ -7225,12 +7249,12 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans,
> u64 bytenr, u64 num_bytes, u64 parent, u64 root_objectid,
> u64 owner, u64 offset)
> {
> + int old_ref_mod, new_ref_mod;
> int ret;
>
> if (btrfs_is_testing(fs_info))
> return 0;
>
> - add_pinned_bytes(fs_info, num_bytes, owner, root_objectid);
>
> /*
> * tree log blocks never actually go into the extent allocation
> @@ -7240,19 +7264,25 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans,
> WARN_ON(owner >= BTRFS_FIRST_FREE_OBJECTID);
> /* unlocks the pinned mutex */
> btrfs_pin_extent(fs_info, bytenr, num_bytes, 1);
> + old_ref_mod = new_ref_mod = 0;
> ret = 0;
> } else if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> ret = btrfs_add_delayed_tree_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, (int)owner,
> - BTRFS_DROP_DELAYED_REF, NULL);
> + num_bytes, parent,
> + root_objectid, (int)owner,
> + BTRFS_DROP_DELAYED_REF, NULL,
> + &old_ref_mod, &new_ref_mod);
> } else {
> ret = btrfs_add_delayed_data_ref(fs_info, trans, bytenr,
> - num_bytes,
> - parent, root_objectid, owner,
> - offset, 0,
> - BTRFS_DROP_DELAYED_REF);
> + num_bytes, parent,
> + root_objectid, owner, offset,
> + 0, BTRFS_DROP_DELAYED_REF,
> + &old_ref_mod, &new_ref_mod);
> }
> +
> + if (ret == 0 && old_ref_mod >= 0 && new_ref_mod < 0)
> + add_pinned_bytes(fs_info, num_bytes, owner, root_objectid);
> +
> return ret;
> }
>
> @@ -8199,9 +8229,9 @@ int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
> BUG_ON(root_objectid == BTRFS_TREE_LOG_OBJECTID);
>
> ret = btrfs_add_delayed_data_ref(fs_info, trans, ins->objectid,
> - ins->offset, 0,
> - root_objectid, owner, offset,
> - ram_bytes, BTRFS_ADD_DELAYED_EXTENT);
> + ins->offset, 0, root_objectid, owner,
> + offset, ram_bytes,
> + BTRFS_ADD_DELAYED_EXTENT, NULL, NULL);
> return ret;
> }
>
> @@ -8421,11 +8451,11 @@ struct extent_buffer *btrfs_alloc_tree_block(struct btrfs_trans_handle *trans,
> extent_op->is_data = false;
> extent_op->level = level;
>
> - ret = btrfs_add_delayed_tree_ref(fs_info, trans,
> - ins.objectid, ins.offset,
> - parent, root_objectid, level,
> + ret = btrfs_add_delayed_tree_ref(fs_info, trans, ins.objectid,
> + ins.offset, parent,
> + root_objectid, level,
> BTRFS_ADD_DELAYED_EXTENT,
> - extent_op);
> + extent_op, NULL, NULL);
> if (ret)
> goto out_free_delayed;
> }
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH] Btrfs: skip commit transaction if we don't have enough pinned bytes
2017-06-06 4:29 ` Liu Bo
@ 2017-06-06 23:47 ` Omar Sandoval
0 siblings, 0 replies; 9+ messages in thread
From: Omar Sandoval @ 2017-06-06 23:47 UTC (permalink / raw)
To: Liu Bo; +Cc: linux-btrfs
On Mon, Jun 05, 2017 at 09:29:47PM -0700, Liu Bo wrote:
> On Fri, Jun 02, 2017 at 11:14:13AM -0700, Omar Sandoval wrote:
> > On Fri, May 19, 2017 at 11:39:15AM -0600, Liu Bo wrote:
> > > We commit transaction in order to reclaim space from pinned bytes because
> > > it could process delayed refs, and in may_commit_transaction(), we check
> > > first if pinned bytes are enough for the required space, we then check if
> > > that plus bytes reserved for delayed insert are enough for the required
> > > space.
> > >
> > > This changes the code to the above logic.
> > >
> > > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > > ---
> > > fs/btrfs/extent-tree.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> > > index e390451c72e6..bded1ddd1bb6 100644
> > > --- a/fs/btrfs/extent-tree.c
> > > +++ b/fs/btrfs/extent-tree.c
> > > @@ -4837,7 +4837,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> > >
> > > spin_lock(&delayed_rsv->lock);
> > > if (percpu_counter_compare(&space_info->total_bytes_pinned,
> > > - bytes - delayed_rsv->size) >= 0) {
> > > + bytes - delayed_rsv->size) < 0) {
> > > spin_unlock(&delayed_rsv->lock);
> > > return -ENOSPC;
> > > }
> >
> > I found this bug in my latest enospc investigation, too. However, the
> > total_bytes_pinned counter is pretty broken. E.g., on my laptop:
> >
> > $ sync; grep -H '' /sys/fs/btrfs/*/allocation/*/total_bytes_pinned
> > /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/data/total_bytes_pinned:48693501952
> > /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/metadata/total_bytes_pinned:-258146304
> > /sys/fs/btrfs/f31cc926-37d3-442d-b50a-10c62d47badc/allocation/system/total_bytes_pinned:0
> >
> > I have a patch to fix it that I haven't cleaned up yet, below. Without
> > it, Bo's fix will probably cause early ENOSPCs. Dave, should we pull
> > Bo's patch out of for-next? In any case, I'll get my fix sent out.
> >
>
> When data delayed refs are not merged, __btrfs_free_extent() will dec
> the pinned as expected, but when they got merged, %pinned bytes only
> got inc'd but not dec'd because the delayed ref has been deleted due
> to ref_count == 0.
>
> This doesn't happen to tree block ref since tree block ref doesn't
> have more than one ref, so ref_mod is either 1 or -1, and tree block
> ref gets removed via btrfs_free_tree_block(), which also needs to be
> changed.
>
> Based on that, I think we can solve the problem by touching
> btrfs_free_tree_block() and data delayed ref instead of head ref.
>
> thanks,
> -liubo
I just sent out the fixes split up into separate patches, so hopefully
the different bugs should be more clear.
^ permalink raw reply [flat|nested] 9+ messages in thread