[10/12] xfs: make xfs_*read_agf return EAGAIN to ALLOC_FLAG_TRYLOCK callers
diff mbox series

Message ID 157984320125.3139258.966527323692871610.stgit@magnolia
State Accepted
Headers show
Series
  • xfs: make buffer functions return error codes
Related show

Commit Message

Darrick J. Wong Jan. 24, 2020, 5:20 a.m. UTC
From: Darrick J. Wong <darrick.wong@oracle.com>

Refactor xfs_read_agf and xfs_alloc_read_agf to return EAGAIN if the
caller passed TRYLOCK and we weren't able to get the lock; and change
the callers to recognize this.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_alloc.c |   36 ++++++++++++++----------------------
 fs/xfs/libxfs/xfs_bmap.c  |   11 ++++++-----
 fs/xfs/xfs_filestream.c   |   11 +++++------
 3 files changed, 25 insertions(+), 33 deletions(-)

Comments

Dave Chinner Jan. 24, 2020, 10:07 p.m. UTC | #1
On Thu, Jan 23, 2020 at 09:20:01PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Refactor xfs_read_agf and xfs_alloc_read_agf to return EAGAIN if the
> caller passed TRYLOCK and we weren't able to get the lock; and change
> the callers to recognize this.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_alloc.c |   36 ++++++++++++++----------------------
>  fs/xfs/libxfs/xfs_bmap.c  |   11 ++++++-----
>  fs/xfs/xfs_filestream.c   |   11 +++++------
>  3 files changed, 25 insertions(+), 33 deletions(-)

The alloc flag assert changes make the error handling much simpler
:)

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Christoph Hellwig Jan. 24, 2020, 11:12 p.m. UTC | #2
On Thu, Jan 23, 2020 at 09:20:01PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Refactor xfs_read_agf and xfs_alloc_read_agf to return EAGAIN if the
> caller passed TRYLOCK and we weren't able to get the lock; and change
> the callers to recognize this.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_alloc.c |   36 ++++++++++++++----------------------
>  fs/xfs/libxfs/xfs_bmap.c  |   11 ++++++-----
>  fs/xfs/xfs_filestream.c   |   11 +++++------
>  3 files changed, 25 insertions(+), 33 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 34b65635ee34..d8053bc96c4d 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2502,12 +2502,11 @@ xfs_alloc_fix_freelist(
>  
>  	if (!pag->pagf_init) {
>  		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
> -		if (error)
> +		if (error) {
> +			/* Couldn't lock the AGF so skip this AG. */
> +			if (error == -EAGAIN)
> +				error = 0;
>  			goto out_no_agbp;
> -		if (!pag->pagf_init) {
> -			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
> -			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
> -			goto out_agbp_relse;
>  		}
>  	}
>  
> @@ -2533,11 +2532,10 @@ xfs_alloc_fix_freelist(
>  	 */
>  	if (!agbp) {
>  		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
> -		if (error)
> -			goto out_no_agbp;
> -		if (!agbp) {
> -			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
> -			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
> +		if (error) {
> +			/* Couldn't lock the AGF so skip this AG. */
> +			if (error == -EAGAIN)
> +				error = 0;
>  			goto out_no_agbp;
>  		}
>  	}
> @@ -2768,11 +2766,10 @@ xfs_alloc_pagf_init(
>  	xfs_buf_t		*bp;
>  	int			error;
>  
> -	if ((error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp)))
> -		return error;
> -	if (bp)
> +	error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp);
> +	if (!error)
>  		xfs_trans_brelse(tp, bp);
> -	return 0;
> +	return error;
>  }
>  
>  /*
> @@ -2961,12 +2958,6 @@ xfs_read_agf(
>  	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
>  			XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
>  			XFS_FSS_TO_BB(mp, 1), flags, bpp, &xfs_agf_buf_ops);
> -	/*
> -	 * Callers of xfs_read_agf() currently interpret a NULL bpp as EAGAIN
> -	 * and need to be converted to check for EAGAIN specifically.
> -	 */
> -	if (error == -EAGAIN)
> -		return 0;
>  	if (error)
>  		return error;
>  
> @@ -2992,14 +2983,15 @@ xfs_alloc_read_agf(
>  
>  	trace_xfs_alloc_read_agf(mp, agno);
>  
> +	/* We don't support trylock when freeing. */
> +	ASSERT((flags & (XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK)) !=
> +			(XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK));

Does this assert really work?  Shouldn't it be

	ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING) ||
	       !(flags & XFS_ALLOC_FLAG_TRYLOCK));

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
Christoph Hellwig Jan. 26, 2020, 2:43 a.m. UTC | #3
On Fri, Jan 24, 2020 at 03:12:07PM -0800, Christoph Hellwig wrote:
> > +	/* We don't support trylock when freeing. */
> > +	ASSERT((flags & (XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK)) !=
> > +			(XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK));
> 
> Does this assert really work?  Shouldn't it be
> 
> 	ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING) ||
> 	       !(flags & XFS_ALLOC_FLAG_TRYLOCK));

Actually, I'll take that back - your version is doing the right thing.
It just isn't quite as obvious to read.

Patch
diff mbox series

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 34b65635ee34..d8053bc96c4d 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2502,12 +2502,11 @@  xfs_alloc_fix_freelist(
 
 	if (!pag->pagf_init) {
 		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
-		if (error)
+		if (error) {
+			/* Couldn't lock the AGF so skip this AG. */
+			if (error == -EAGAIN)
+				error = 0;
 			goto out_no_agbp;
-		if (!pag->pagf_init) {
-			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
-			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
-			goto out_agbp_relse;
 		}
 	}
 
@@ -2533,11 +2532,10 @@  xfs_alloc_fix_freelist(
 	 */
 	if (!agbp) {
 		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
-		if (error)
-			goto out_no_agbp;
-		if (!agbp) {
-			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
-			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
+		if (error) {
+			/* Couldn't lock the AGF so skip this AG. */
+			if (error == -EAGAIN)
+				error = 0;
 			goto out_no_agbp;
 		}
 	}
@@ -2768,11 +2766,10 @@  xfs_alloc_pagf_init(
 	xfs_buf_t		*bp;
 	int			error;
 
-	if ((error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp)))
-		return error;
-	if (bp)
+	error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp);
+	if (!error)
 		xfs_trans_brelse(tp, bp);
-	return 0;
+	return error;
 }
 
 /*
@@ -2961,12 +2958,6 @@  xfs_read_agf(
 	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
 			XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
 			XFS_FSS_TO_BB(mp, 1), flags, bpp, &xfs_agf_buf_ops);
-	/*
-	 * Callers of xfs_read_agf() currently interpret a NULL bpp as EAGAIN
-	 * and need to be converted to check for EAGAIN specifically.
-	 */
-	if (error == -EAGAIN)
-		return 0;
 	if (error)
 		return error;
 
@@ -2992,14 +2983,15 @@  xfs_alloc_read_agf(
 
 	trace_xfs_alloc_read_agf(mp, agno);
 
+	/* We don't support trylock when freeing. */
+	ASSERT((flags & (XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK)) !=
+			(XFS_ALLOC_FLAG_FREEING | XFS_ALLOC_FLAG_TRYLOCK));
 	ASSERT(agno != NULLAGNUMBER);
 	error = xfs_read_agf(mp, tp, agno,
 			(flags & XFS_ALLOC_FLAG_TRYLOCK) ? XBF_TRYLOCK : 0,
 			bpp);
 	if (error)
 		return error;
-	if (!*bpp)
-		return 0;
 	ASSERT(!(*bpp)->b_error);
 
 	agf = XFS_BUF_TO_AGF(*bpp);
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index cfcef076c72f..9a6d7a84689a 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3311,11 +3311,12 @@  xfs_bmap_longest_free_extent(
 	pag = xfs_perag_get(mp, ag);
 	if (!pag->pagf_init) {
 		error = xfs_alloc_pagf_init(mp, tp, ag, XFS_ALLOC_FLAG_TRYLOCK);
-		if (error)
-			goto out;
-
-		if (!pag->pagf_init) {
-			*notinit = 1;
+		if (error) {
+			/* Couldn't lock the AGF, so skip this AG. */
+			if (error == -EAGAIN) {
+				*notinit = 1;
+				error = 0;
+			}
 			goto out;
 		}
 	}
diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index 5f12b5d8527a..1a88025e68a3 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -159,16 +159,15 @@  xfs_filestream_pick_ag(
 
 		if (!pag->pagf_init) {
 			err = xfs_alloc_pagf_init(mp, NULL, ag, trylock);
-			if (err && !trylock) {
+			if (err) {
 				xfs_perag_put(pag);
-				return err;
+				if (err != -EAGAIN)
+					return err;
+				/* Couldn't lock the AGF, skip this AG. */
+				continue;
 			}
 		}
 
-		/* Might fail sometimes during the 1st pass with trylock set. */
-		if (!pag->pagf_init)
-			goto next_ag;
-
 		/* Keep track of the AG with the most free blocks. */
 		if (pag->pagf_freeblks > maxfree) {
 			maxfree = pag->pagf_freeblks;