xfs: make xfs_*read_agf return EAGAIN to ALLOC_FLAG_TRYLOCK callers

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>

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 34b65635ee34d16553ab1ef8bac1cdb14479f8cf..d8053bc96c4d2393093ab74d354ff1f9c44aac0d 100644 (file)
--- 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 cfcef076c72f0b34d4df91c763ca369ba0e9f033..9a6d7a84689abd37dbb6a8b7894f224ad0796671 100644 (file)
--- 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 5f12b5d8527a93d9a0fc50764dfa2dde138bd1c7..1a88025e68a3a73a637f8824890961ed0f0ac4c0 100644 (file)
--- 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;