Function unpin_extent_cache() doesn't propagate an error if the call to
lookup_extent_mapping() fails. This patch adds an error return (EINVAL)
and simply logs it in the only caller.
Signed-off-by: Luís Henriques <[email protected]>
---
Hi!
As per David and Johannes reviews, I'm now proposing a different approach.
Note that I kept the WARN_ON() instead of replacing it by an ASSERT(). In
fact, I considered removing the WARN_ON() completely and simply return the
error if em->start != start. But I guess it may useful for debug.
Changes since v1:
Instead of changing unpin_extent_cache() into a void function, make it
propage an error code instead.
fs/btrfs/extent_map.c | 4 +++-
fs/btrfs/inode.c | 8 ++++++--
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 0cdb3e86f29b..f4e7956edc05 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -304,8 +304,10 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
WARN_ON(!em || em->start != start);
- if (!em)
+ if (!em) {
+ ret = -EINVAL;
goto out;
+ }
em->generation = gen;
clear_bit(EXTENT_FLAG_PINNED, &em->flags);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index dbbb67293e34..21eb66fcc0df 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3273,8 +3273,12 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
ordered_extent->disk_num_bytes);
}
}
- unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
- ordered_extent->num_bytes, trans->transid);
+
+ /* Proceed even if we fail to unpin extent from cache */
+ if (unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
+ ordered_extent->num_bytes, trans->transid) < 0)
+ btrfs_warn(fs_info, "failed to unpin extent from cache");
+
if (ret < 0) {
btrfs_abort_transaction(trans, ret);
goto out;
On Thu, Jul 20, 2023 at 5:05 PM Luís Henriques <[email protected]> wrote:
>
> Function unpin_extent_cache() doesn't propagate an error if the call to
> lookup_extent_mapping() fails. This patch adds an error return (EINVAL)
> and simply logs it in the only caller.
>
> Signed-off-by: Luís Henriques <[email protected]>
> ---
> Hi!
>
> As per David and Johannes reviews, I'm now proposing a different approach.
> Note that I kept the WARN_ON() instead of replacing it by an ASSERT(). In
> fact, I considered removing the WARN_ON() completely and simply return the
> error if em->start != start. But I guess it may useful for debug.
>
> Changes since v1:
> Instead of changing unpin_extent_cache() into a void function, make it
> propage an error code instead.
>
> fs/btrfs/extent_map.c | 4 +++-
> fs/btrfs/inode.c | 8 ++++++--
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> index 0cdb3e86f29b..f4e7956edc05 100644
> --- a/fs/btrfs/extent_map.c
> +++ b/fs/btrfs/extent_map.c
> @@ -304,8 +304,10 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
>
> WARN_ON(!em || em->start != start);
>
> - if (!em)
> + if (!em) {
> + ret = -EINVAL;
> goto out;
> + }
>
> em->generation = gen;
> clear_bit(EXTENT_FLAG_PINNED, &em->flags);
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index dbbb67293e34..21eb66fcc0df 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3273,8 +3273,12 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
> ordered_extent->disk_num_bytes);
> }
> }
> - unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
> - ordered_extent->num_bytes, trans->transid);
> +
> + /* Proceed even if we fail to unpin extent from cache */
> + if (unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
> + ordered_extent->num_bytes, trans->transid) < 0)
> + btrfs_warn(fs_info, "failed to unpin extent from cache");
Well, this is not very useful. It doesn't provide any more useful
information than what we get from the WARN_ON() at
unpin_extent_cache(), making the patch not useful.
This warning has actually happened a few times when running fstests
that exercise relocation (not sure if it's gone and accidently fixed
by something recently).
But to make this more useful, I would place the message at
unpin_extent_cache() with useful information such as:
- inode number
- id of the root the inode belongs to
- the file offset (the start argument) and extent length (or end offset)
- why the warning triggered: we didn't find the extent map or we found
one with a different start offset
- if we found an unexpected extent map, dump its flags (so we can see
if it happens only with compressed or prealloc extents for e.g.) and
other details (length/end offset for e.g.)
Thanks.
> +
> if (ret < 0) {
> btrfs_abort_transaction(trans, ret);
> goto out;
Filipe Manana <[email protected]> writes:
> On Thu, Jul 20, 2023 at 5:05 PM Luís Henriques <[email protected]> wrote:
>>
>> Function unpin_extent_cache() doesn't propagate an error if the call to
>> lookup_extent_mapping() fails. This patch adds an error return (EINVAL)
>> and simply logs it in the only caller.
>>
>> Signed-off-by: Luís Henriques <[email protected]>
>> ---
>> Hi!
>>
>> As per David and Johannes reviews, I'm now proposing a different approach.
>> Note that I kept the WARN_ON() instead of replacing it by an ASSERT(). In
>> fact, I considered removing the WARN_ON() completely and simply return the
>> error if em->start != start. But I guess it may useful for debug.
>>
>> Changes since v1:
>> Instead of changing unpin_extent_cache() into a void function, make it
>> propage an error code instead.
>>
>> fs/btrfs/extent_map.c | 4 +++-
>> fs/btrfs/inode.c | 8 ++++++--
>> 2 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
>> index 0cdb3e86f29b..f4e7956edc05 100644
>> --- a/fs/btrfs/extent_map.c
>> +++ b/fs/btrfs/extent_map.c
>> @@ -304,8 +304,10 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
>>
>> WARN_ON(!em || em->start != start);
>>
>> - if (!em)
>> + if (!em) {
>> + ret = -EINVAL;
>> goto out;
>> + }
>>
>> em->generation = gen;
>> clear_bit(EXTENT_FLAG_PINNED, &em->flags);
>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>> index dbbb67293e34..21eb66fcc0df 100644
>> --- a/fs/btrfs/inode.c
>> +++ b/fs/btrfs/inode.c
>> @@ -3273,8 +3273,12 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
>> ordered_extent->disk_num_bytes);
>> }
>> }
>> - unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
>> - ordered_extent->num_bytes, trans->transid);
>> +
>> + /* Proceed even if we fail to unpin extent from cache */
>> + if (unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
>> + ordered_extent->num_bytes, trans->transid) < 0)
>> + btrfs_warn(fs_info, "failed to unpin extent from cache");
>
> Well, this is not very useful. It doesn't provide any more useful
> information than what we get from the WARN_ON() at
> unpin_extent_cache(), making the patch not useful.
>
> This warning has actually happened a few times when running fstests
> that exercise relocation (not sure if it's gone and accidently fixed
> by something recently).
Oh! In that case replacing the WARN_ON() by an ASSERT() would have
definitely be a bad idea.
> But to make this more useful, I would place the message at
> unpin_extent_cache() with useful information such as:
>
> - inode number
> - id of the root the inode belongs to
> - the file offset (the start argument) and extent length (or end offset)
> - why the warning triggered: we didn't find the extent map or we found
> one with a different start offset
> - if we found an unexpected extent map, dump its flags (so we can see
> if it happens only with compressed or prealloc extents for e.g.) and
> other details (length/end offset for e.g.)
Thanks, Filipe. This all makes sense. And in this case I guess I should
go back to the initial approach of changing the function to a void
function, but adding all this useful information.
Cheers,
--
Luís