[SRU][jammy PATCH v3 1/1] NFS: nfs_async_write_reschedule_io must not recurse into the writeback code

[Magali Lemes]

Sorry for the delay reviewing this one.

On 16/12/2024 16:40, Mike Snitzer wrote:
> From: Trond Myklebust <trond.myklebust at hammerspace.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2089410
> 
> commit 31545f4b7cdb6da6a0519120b8c96dc40f186aac upstream stable/linux-5.15.y.

This should remain exactly as in the original commit you're picking. No 
need for changes here, so it should just be `commit 
b1a28f2eb9ea7a5a1763fe53fe699aa0feae4231 upstream.`.

> 
> It is not safe to call filemap_fdatawrite_range() from
> nfs_async_write_reschedule_io(), since we're often calling from a page
> reclaim context. Just let fsync() redrive the writeback for us.
> 
> Signed-off-by: Trond Myklebust <trond.myklebust at hammerspace.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> (cherry picked from commit 31545f4b7cdb6da6a0519120b8c96dc40f186aac)

Since you're now picking the commit from upstream stable, that line 
should read (cherry picked from commit 
31545f4b7cdb6da6a0519120b8c96dc40f186aac linux-5.15.y).

> Fixes: 7be7b3ca16a59 ("NFS: Ensure we immediately start writeback on rescheduled writes")
> Link: https://lore.kernel.org/stable/2024112146-tiptoeing-available-c5fe@gregkh/T/
> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2089410

I don't think we strictly need these 3 extra lines above that don't 
exist in the original commit.

> Signed-off-by: Mike Snitzer <snitzer at hammerspace.com>
> Signed-off-by: Mike Snitzer <snitzer at kernel.org>
> ---
>   fs/nfs/write.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index 2e1c45344d1fd..00e11c6602fe4 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1437,8 +1437,6 @@ static void nfs_async_write_error(struct list_head *head, int error)
>   static void nfs_async_write_reschedule_io(struct nfs_pgio_header *hdr)
>   {
>   	nfs_async_write_error(&hdr->pages, 0);
> -	filemap_fdatawrite_range(hdr->inode->i_mapping, hdr->args.offset,
> -			hdr->args.offset + hdr->args.count - 1);
>   }
>   
>   static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops = {

In summary, cherry pick the commit appending the `(cherry picked from 
<hash> linux-5.15.y)` line, add the Launchpad BugLink immediately after 
the commit subject (exactly as you did) and add your Signed-off-by line 
right below the `(cherry picked from)` line.
Also, could you send the patch in reply to the cover letter?


Magali