Re: [PATCH v3 1/5] zonefs: pass GFP_KERNEL to blkdev_zone_mgmt() call

Damien Le Moal
2024-02-09T07:44:27Z

On 1/29/24 16:52, 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.
>
> Link: https://lore.kernel.org/all/ZZcgXI46AinlcBDP@casper.infradead.org/
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
> 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",
>

Given that zonefs_inode_zone_mgmt() which calls zonefs_zone_mgmt() is only used
for sequential zone inodes, and that these inodes cannot be written with
buffered IOs, I think this is safe as we will never have dirty pages to
writeback for reclaim. So there should be no risk of re-entering the FS on
reclaim with GFP_KERNEL.

So:

Acked-by: Damien Le Moal <dlemoal@kernel.org>

--
Damien Le Moal
Western Digital Research