Re: [PATCH 7/9] ext4: Move percpu_rwsem protection into ext4_writepages()

Ritesh Harjani (IBM)
2022-12-01T11:20:38Z

On 22/11/30 05:35PM, Jan Kara wrote:
> Move protection by percpu_rwsem from ext4_do_writepages() to
> ext4_writepages(). We will not want to grab this protection during
> transaction commits as that would be prone to deadlocks and the
> protection is not needed. Move the shutdown state checking as well since
> we want to be able to complete commit while the shutdown is in progress.

Yup. Sounds good. Please feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/ext4/inode.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index fbea77ab470f..00c4d12f8270 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2718,10 +2718,6 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
> struct blk_plug plug;
> bool give_up_on_write = false;
>
> - if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
> - return -EIO;
> -
> - percpu_down_read(&sbi->s_writepages_rwsem);
> trace_ext4_writepages(inode, wbc);
>
> /*
> @@ -2930,20 +2926,28 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
> out_writepages:
> trace_ext4_writepages_result(inode, wbc, ret,
> nr_to_write - wbc->nr_to_write);
> - percpu_up_read(&sbi->s_writepages_rwsem);
> return ret;
> }
>
> static int ext4_writepages(struct address_space *mapping,
> struct writeback_control *wbc)
> {
> + struct super_block *sb = mapping->host->i_sb;
> struct mpage_da_data mpd = {
> .inode = mapping->host,
> .wbc = wbc,
> .can_map = 1,
> };
> + int ret;
> +
> + if (unlikely(ext4_forced_shutdown(EXT4_SB(sb))))
> + return -EIO;
>
> - return ext4_do_writepages(&mpd);
> + percpu_down_read(&EXT4_SB(sb)->s_writepages_rwsem);
> + ret = ext4_do_writepages(&mpd);
> + percpu_up_read(&EXT4_SB(sb)->s_writepages_rwsem);
> +
> + return ret;
> }
>
> static int ext4_dax_writepages(struct address_space *mapping,
> --
> 2.35.3
>