Re: [PATCH 2/2] nfs: refactor pNFS functions using clear_and_wake_up_bit

[Agatha Isabelle Moreira]

On Mon, Jun 22, 2026 at 07:55:11PM +0200, Arnaud Bonnet wrote:
> Commit 8236b0ae31c83 ("bdi: wake up concurrent wb_shutdown() callers.")
> introduces the clear_and_wake_up_bit() helper as a wrapper for the
> common clear -> barrier -> wake up bitops sequence.
> 
> The file pnfs.c has several helpers with identical contents. Thus they
> are replaced with the more recent clean_and_wake_up_bit() global helper
> which describes accurately its effects at the call and still specifies
> the cleared bit. This also homogenizes the code with other subsystems.
> 
> Since the helpers are no longer used after this, they can be safely
> removed.


Hi Arnaud!

> 
> Suggested-by: Agatha Isabelle Moreira <code@xxxxxxxxxx>
> Link: https://kernelnewbies.org/Beginner%20Cleanup%20and%20Refactor%20Tasks%20by%20Agatha%20Isabelle%20Moreira#task_007
> Signed-off-by: Arnaud Bonnet <abo@xxxxxxxxxxx>
> ---
>  fs/nfs/pnfs.c | 35 ++++++++++-------------------------
>  1 file changed, 10 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 743467e9ba20..96ee18af1ebf 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -2100,15 +2100,6 @@ static bool pnfs_is_first_layoutget(struct pnfs_layout_hdr *lo)
>  	return test_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags);
>  }
>  
> -static void pnfs_clear_first_layoutget(struct pnfs_layout_hdr *lo)
> -{
> -	unsigned long *bitlock = &lo->plh_flags;
> -
> -	clear_bit_unlock(NFS_LAYOUT_FIRST_LAYOUTGET, bitlock);
> -	smp_mb__after_atomic();
> -	wake_up_bit(bitlock, NFS_LAYOUT_FIRST_LAYOUTGET);
> -}

I noticed that you found a subsystem function doing something quite
similar to what the `clear_and_wake_up_bit()` function.

>From the cleanup point of view it seems good to me, but I think some
input from someone in the nfs subsystem would be highly appreciated to
confirm the correctness of this refactor.

IDK if you considered or if this makes total sense, but my only concern
here is that the maintainer *could* find the replaced function
`pnfs_clear_first_layoutget()` preferable to be kept, since it carries
some subsystem semantics (the `struct pnfs_layout_hdr *lo` argument and
the NFS_LAYOUT_FIRST_LAYOUTGET bit). But I could also be completely
wrong.

In the event that `NFS_LAYOUT_FIRST_LAYOUTGET` gets replaced by another
constant in the future (IDK if this is a plausible possibility), by
keeping the original function there would be only a single place to
touch.

Let's hope this message attracts more comments from someone with the
subsystem's expertise, which would be highly appreciated.

> -
>  static void _add_to_server_list(struct pnfs_layout_hdr *lo,
>  				struct nfs_server *server)
>  {
> @@ -2284,7 +2275,8 @@ pnfs_update_layout(struct inode *ino,
>  					iomode, lo, lseg,
>  					PNFS_UPDATE_LAYOUT_INVALID_OPEN);
>  			nfs4_schedule_stateid_recovery(server, ctx->state);
> -			pnfs_clear_first_layoutget(lo);
> +			clear_and_wake_up_bit(NFS_LAYOUT_FIRST_LAYOUTGET,
> +				&lo->plh_flags);
>  			pnfs_put_layout_hdr(lo);
>  			goto lookup_again;
>  		}
> @@ -2353,7 +2345,8 @@ pnfs_update_layout(struct inode *ino,
>  			if (!exception.retry)
>  				goto out_put_layout_hdr;
>  			if (first)
> -				pnfs_clear_first_layoutget(lo);
> +				clear_and_wake_up_bit(NFS_LAYOUT_FIRST_LAYOUTGET,
> +					&lo->plh_flags);
>  			trace_pnfs_update_layout(ino, pos, count,
>  				iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
>  			pnfs_put_layout_hdr(lo);
> @@ -2365,7 +2358,7 @@ pnfs_update_layout(struct inode *ino,
>  
>  out_put_layout_hdr:
>  	if (first)
> -		pnfs_clear_first_layoutget(lo);
> +		clear_and_wake_up_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags);
>  	trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
>  				 PNFS_UPDATE_LAYOUT_EXIT);
>  	pnfs_put_layout_hdr(lo);
> @@ -2457,7 +2450,7 @@ static void _lgopen_prepare_attached(struct nfs4_opendata *data,
>  	lgp = pnfs_alloc_init_layoutget_args(ino, ctx, &current_stateid, &rng,
>  					     nfs_io_gfp_mask());
>  	if (!lgp) {
> -		pnfs_clear_first_layoutget(lo);
> +		clear_and_wake_up_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags);
>  		nfs_layoutget_end(lo);
>  		pnfs_put_layout_hdr(lo);
>  		return;
> @@ -2561,7 +2554,8 @@ void nfs4_lgopen_release(struct nfs4_layoutget *lgp)
>  {
>  	if (lgp != NULL) {
>  		if (lgp->lo) {
> -			pnfs_clear_first_layoutget(lgp->lo);
> +			clear_and_wake_up_bit(NFS_LAYOUT_FIRST_LAYOUTGET,
> +				&lgp->lo->plh_flags);
>  			nfs_layoutget_end(lgp->lo);
>  		}
>  		pnfs_layoutget_free(lgp);
> @@ -3273,15 +3267,6 @@ pnfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
>  }
>  EXPORT_SYMBOL_GPL(pnfs_generic_pg_readpages);
>  
> -static void pnfs_clear_layoutcommitting(struct inode *inode)
> -{
> -	unsigned long *bitlock = &NFS_I(inode)->flags;
> -
> -	clear_bit_unlock(NFS_INO_LAYOUTCOMMITTING, bitlock);
> -	smp_mb__after_atomic();
> -	wake_up_bit(bitlock, NFS_INO_LAYOUTCOMMITTING);
> -}
> -
>  /*
>   * There can be multiple RW segments.
>   */
> @@ -3306,7 +3291,7 @@ static void pnfs_list_write_lseg_done(struct inode *inode, struct list_head *lis
>  		pnfs_put_lseg(lseg);
>  	}
>  
> -	pnfs_clear_layoutcommitting(inode);
> +	clear_and_wake_up_bit(NFS_INO_LAYOUTCOMMITTING, &NFS_I(inode)->flags);
>  }
>  
>  void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg)
> @@ -3446,7 +3431,7 @@ pnfs_layoutcommit_inode(struct inode *inode, bool sync)
>  	spin_unlock(&inode->i_lock);
>  	kfree(data);
>  clear_layoutcommitting:
> -	pnfs_clear_layoutcommitting(inode);
> +	clear_and_wake_up_bit(NFS_INO_LAYOUTCOMMITTING, &NFS_I(inode)->flags);
>  	goto out;
>  }
>  EXPORT_SYMBOL_GPL(pnfs_layoutcommit_inode);
> -- 
> 2.53.0
> 

Other than that, both patches appear to successfuly apply and compile
just fine.

-- 
Agatha Isabelle Moreira
Systems Engineer | C