[PATCH] btrfs: fix uninitialized return value from btrfs_reclaim_sweep()

[PATCH] btrfs: fix uninitialized return value from btrfs_reclaim_sweep()

[fdmanana]

From: Filipe Manana <fdmanana@suse.com>

The return variable 'ret' at btrfs_reclaim_sweep() is never assigned if
none of the space infos is reclaimable (for example if periodic reclaim
is disabled, which is the default), so we return an undefined value.

This can be fixed my making btrfs_reclaim_sweep() not return any value
as well as do_reclaim_sweep() because:

1) do_reclaim_sweep() always returns 0, so we can make it return void;

2) The only caller of btrfs_reclaim_sweep() (btrfs_reclaim_bgs()) doesn't
   care about its return value, and in its context there's nothing to do
   about any errors anyway.

Therefore return the return value from btrfs_reclaim_sweep() and
do_reclaim_sweep().

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/space-info.c | 17 +++++------------
 fs/btrfs/space-info.h |  2 +-
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 68e14fd48638..c691784b4660 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1985,8 +1985,8 @@ static bool is_reclaim_urgent(struct btrfs_space_info *space_info)
 	return unalloc < data_chunk_size;
 }
 
-static int do_reclaim_sweep(struct btrfs_fs_info *fs_info,
-			    struct btrfs_space_info *space_info, int raid)
+static void do_reclaim_sweep(struct btrfs_fs_info *fs_info,
+			     struct btrfs_space_info *space_info, int raid)
 {
 	struct btrfs_block_group *bg;
 	int thresh_pct;
@@ -2031,7 +2031,6 @@ static int do_reclaim_sweep(struct btrfs_fs_info *fs_info,
 	}
 
 	up_read(&space_info->groups_sem);
-	return 0;
 }
 
 void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s64 bytes)
@@ -2074,21 +2073,15 @@ bool btrfs_should_periodic_reclaim(struct btrfs_space_info *space_info)
 	return ret;
 }
 
-int btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info)
+void btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info)
 {
-	int ret;
 	int raid;
 	struct btrfs_space_info *space_info;
 
 	list_for_each_entry(space_info, &fs_info->space_info, list) {
 		if (!btrfs_should_periodic_reclaim(space_info))
 			continue;
-		for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++) {
-			ret = do_reclaim_sweep(fs_info, space_info, raid);
-			if (ret)
-				return ret;
-		}
+		for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++)
+			do_reclaim_sweep(fs_info, space_info, raid);
 	}
-
-	return ret;
 }
diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
index 88b44221ce97..5602026c5e14 100644
--- a/fs/btrfs/space-info.h
+++ b/fs/btrfs/space-info.h
@@ -294,6 +294,6 @@ void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s6
 void btrfs_set_periodic_reclaim_ready(struct btrfs_space_info *space_info, bool ready);
 bool btrfs_should_periodic_reclaim(struct btrfs_space_info *space_info);
 int btrfs_calc_reclaim_threshold(struct btrfs_space_info *space_info);
-int btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info);
+void btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info);
 
 #endif /* BTRFS_SPACE_INFO_H */
-- 
2.43.0

Re: [PATCH] btrfs: fix uninitialized return value from btrfs_reclaim_sweep()

[Filipe Manana]

On Tue, Aug 27, 2024 at 11:41 AM <fdmanana@kernel.org> wrote:
>
> From: Filipe Manana <fdmanana@suse.com>
>
> The return variable 'ret' at btrfs_reclaim_sweep() is never assigned if
> none of the space infos is reclaimable (for example if periodic reclaim
> is disabled, which is the default), so we return an undefined value.
>
> This can be fixed my making btrfs_reclaim_sweep() not return any value
> as well as do_reclaim_sweep() because:
>
> 1) do_reclaim_sweep() always returns 0, so we can make it return void;
>
> 2) The only caller of btrfs_reclaim_sweep() (btrfs_reclaim_bgs()) doesn't
>    care about its return value, and in its context there's nothing to do
>    about any errors anyway.
>
> Therefore return the return value from btrfs_reclaim_sweep() and

The first "return" should be "remove", I'll amend that when committing
the patch to for-next.

> do_reclaim_sweep().
>
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
>  fs/btrfs/space-info.c | 17 +++++------------
>  fs/btrfs/space-info.h |  2 +-
>  2 files changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index 68e14fd48638..c691784b4660 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -1985,8 +1985,8 @@ static bool is_reclaim_urgent(struct btrfs_space_info *space_info)
>         return unalloc < data_chunk_size;
>  }
>
> -static int do_reclaim_sweep(struct btrfs_fs_info *fs_info,
> -                           struct btrfs_space_info *space_info, int raid)
> +static void do_reclaim_sweep(struct btrfs_fs_info *fs_info,
> +                            struct btrfs_space_info *space_info, int raid)
>  {
>         struct btrfs_block_group *bg;
>         int thresh_pct;
> @@ -2031,7 +2031,6 @@ static int do_reclaim_sweep(struct btrfs_fs_info *fs_info,
>         }
>
>         up_read(&space_info->groups_sem);
> -       return 0;
>  }
>
>  void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s64 bytes)
> @@ -2074,21 +2073,15 @@ bool btrfs_should_periodic_reclaim(struct btrfs_space_info *space_info)
>         return ret;
>  }
>
> -int btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info)
> +void btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info)
>  {
> -       int ret;
>         int raid;
>         struct btrfs_space_info *space_info;
>
>         list_for_each_entry(space_info, &fs_info->space_info, list) {
>                 if (!btrfs_should_periodic_reclaim(space_info))
>                         continue;
> -               for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++) {
> -                       ret = do_reclaim_sweep(fs_info, space_info, raid);
> -                       if (ret)
> -                               return ret;
> -               }
> +               for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++)
> +                       do_reclaim_sweep(fs_info, space_info, raid);
>         }
> -
> -       return ret;
>  }
> diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
> index 88b44221ce97..5602026c5e14 100644
> --- a/fs/btrfs/space-info.h
> +++ b/fs/btrfs/space-info.h
> @@ -294,6 +294,6 @@ void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s6
>  void btrfs_set_periodic_reclaim_ready(struct btrfs_space_info *space_info, bool ready);
>  bool btrfs_should_periodic_reclaim(struct btrfs_space_info *space_info);
>  int btrfs_calc_reclaim_threshold(struct btrfs_space_info *space_info);
> -int btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info);
> +void btrfs_reclaim_sweep(struct btrfs_fs_info *fs_info);
>
>  #endif /* BTRFS_SPACE_INFO_H */
> --
> 2.43.0
>
>

Re: [PATCH] btrfs: fix uninitialized return value from btrfs_reclaim_sweep()

[Josef Bacik]

On Tue, Aug 27, 2024 at 11:41:19AM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The return variable 'ret' at btrfs_reclaim_sweep() is never assigned if
> none of the space infos is reclaimable (for example if periodic reclaim
> is disabled, which is the default), so we return an undefined value.
> 
> This can be fixed my making btrfs_reclaim_sweep() not return any value
> as well as do_reclaim_sweep() because:
> 
> 1) do_reclaim_sweep() always returns 0, so we can make it return void;
> 
> 2) The only caller of btrfs_reclaim_sweep() (btrfs_reclaim_bgs()) doesn't
>    care about its return value, and in its context there's nothing to do
>    about any errors anyway.
> 
> Therefore return the return value from btrfs_reclaim_sweep() and
> do_reclaim_sweep().
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef