[PATCH 13/14] xfs: make xfs_*read_agf return EAGAIN to ALLOC_FLAG_TRYLOCK callers

Darrick J. Wong
2020-02-20T01:46:01Z

Source kernel commit: f48e2df8a877ca1c19d92cfd7e74cc5956fa84cb

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
libxfs/xfs_alloc.c | 36 ++++++++++++++----------------------
libxfs/xfs_bmap.c | 11 ++++++-----
2 files changed, 20 insertions(+), 27 deletions(-)

diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index be1bf736..a92ca524 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -2498,12 +2498,11 @@ 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;
}
}

@@ -2529,11 +2528,10 @@ 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;
}
}
@@ -2764,11 +2762,10 @@ 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;
}

/*
@@ -2957,12 +2954,6 @@ 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;

@@ -2988,14 +2979,15 @@ 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/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index f917a6eb..d43155d0 100644
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -3304,11 +3304,12 @@ 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;
}
}