xfs: fix finding a last resort AG in xfs_filestream_pick_ag

When the main loop in xfs_filestream_pick_ag fails to find a suitable
AG it tries to just pick the online AG.  But the loop for that uses
args->pag as loop iterator while the later code expects pag to be
set.  Fix this by reusing the max_pag case for this last resort, and
also add a check for impossible case of no AG just to make sure that
the uninitialized pag doesn't even escape in theory.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index f523027cc325864753210b9e30b6fed15282e849..ecf8a0f6c1362e0b8a4affaa144e568bd8926004 100644 (file)
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -64,7 +64,7 @@ xfs_filestream_pick_ag(
        struct xfs_perag        *pag;
        struct xfs_perag        *max_pag = NULL;
        xfs_extlen_t            minlen = *longest;
-       xfs_extlen_t            free = 0, minfree, maxfree = 0;
+       xfs_extlen_t            minfree, maxfree = 0;
        xfs_agnumber_t          agno;
        bool                    first_pass = true;
 
@@ -113,7 +113,6 @@ restart:
                             !(flags & XFS_PICK_USERDATA) ||
                             (flags & XFS_PICK_LOWSPACE))) {
                                /* Break out, retaining the reference on the AG. */
-                               free = pag->pagf_freeblks;
                                if (max_pag)
                                        xfs_perag_rele(max_pag);
                                goto done;
@@ -149,18 +148,19 @@ restart:
         * filestream. It none suit, just use whatever AG we can grab.
         */
        if (!max_pag) {
-               for_each_perag_wrap(args->mp, 0, start_agno, args->pag)
+               for_each_perag_wrap(args->mp, 0, start_agno, pag) {
+                       max_pag = pag;
                        break;
-               atomic_inc(&args->pag->pagf_fstrms);
-               *longest = 0;
-       } else {
-               pag = max_pag;
-               free = maxfree;
-               atomic_inc(&pag->pagf_fstrms);
+               }
+               /* Bail if there are no AGs at all to select from. */
+               if (!max_pag)
+                       return -ENOSPC;
        }
 
+       pag = max_pag;
+       atomic_inc(&pag->pagf_fstrms);
 done:
-       trace_xfs_filestream_pick(pag, pino, free);
+       trace_xfs_filestream_pick(pag, pino, pag->pagf_freeblks);
        args->pag = pag;
        return 0;