On Tue, 23 Jan 2024, Johannes Thumshirn wrote:
> Pass GFP_KERNEL instead of GFP_NOFS to the blkdev_zone_mgmt() call in
> zonefs_zone_mgmt().
>
> As as zonefs_zone_mgmt() and zonefs_inode_zone_mgmt() are never called
> from a place that can recurse back into the filesystem on memory reclaim,
> it is save to call blkdev_zone_mgmt() with GFP_KERNEL.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> ---
> fs/zonefs/super.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index 93971742613a..63fbac018c04 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -113,7 +113,7 @@ static int zonefs_zone_mgmt(struct super_block *sb,
>
> trace_zonefs_zone_mgmt(sb, z, op);
> ret = blkdev_zone_mgmt(sb->s_bdev, op, z->z_sector,
> - z->z_size >> SECTOR_SHIFT, GFP_NOFS);
> + z->z_size >> SECTOR_SHIFT, GFP_KERNEL);
> if (ret) {
> zonefs_err(sb,
> "Zone management operation %s at %llu failed %d\n",
>
> --
> 2.43.0
zonefs_inode_zone_mgmt calls
lockdep_assert_held(&ZONEFS_I(inode)->i_truncate_mutex); - so, this
function is called with the mutex held - could it happen that the
GFP_KERNEL allocation recurses into the filesystem and attempts to take
i_truncate_mutex as well?
i.e. GFP_KERNEL -> iomap_do_writepage -> zonefs_write_map_blocks ->
zonefs_write_iomap_begin -> mutex_lock(&zi->i_truncate_mutex)
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