xfs: adjust allocation length in xfs_alloc_space_available

commit 54fee133ad59c87ab01dd84ab3e9397134b32acb upstream.

We must decide in xfs_alloc_fix_freelist if we can perform an
allocation from a given AG is possible or not based on the available
space, and should not fail the allocation past that point on a
healthy file system.

But currently we have two additional places that second-guess
xfs_alloc_fix_freelist: xfs_alloc_ag_vextent tries to adjust the
maxlen parameter to remove the reservation before doing the
allocation (but ignores the various minium freespace requirements),
and xfs_alloc_fix_minleft tries to fix up the allocated length
after we've found an extent, but ignores the reservations and also
doesn't take the AGFL into account (and thus fails allocations
for not matching minlen in some cases).

Remove all these later fixups and just correct the maxlen argument
inside xfs_alloc_fix_freelist once we have the AGF buffer locked.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 18 insertions, 65 deletions

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index fe925702c955..f2e7eb6e5243 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -362,36 +362,12 @@ xfs_alloc_fix_len(
                 return;
         ASSERT(rlen >= args->minlen && rlen <= args->maxlen);
         ASSERT(rlen % args->prod == args->mod);
+        ASSERT(args->pag->pagf_freeblks + args->pag->pagf_flcount >=
+                rlen + args->minleft);
         args->len = rlen;
 }
 
 /*
- * Fix up length if there is too little space left in the a.g.
- * Return 1 if ok, 0 if too little, should give up.
- */
-STATIC int
-xfs_alloc_fix_minleft(
-        xfs_alloc_arg_t *args)          /* allocation argument structure */
-{
-        xfs_agf_t       *agf;           /* a.g. freelist header */
-        int             diff;           /* free space difference */
-
-        if (args->minleft == 0)
-                return 1;
-        agf = XFS_BUF_TO_AGF(args->agbp);
-        diff = be32_to_cpu(agf->agf_freeblks)
-                - args->len - args->minleft;
-        if (diff >= 0)
-                return 1;
-        args->len += diff;              /* shrink the allocated space */
-        /* casts to (int) catch length underflows */
-        if ((int)args->len >= (int)args->minlen)
-                return 1;
-        args->agbno = NULLAGBLOCK;
-        return 0;
-}
-
-/*
  * Update the two btrees, logically removing from freespace the extent
  * starting at rbno, rlen blocks.  The extent is contained within the
  * actual (current) free extent fbno for flen blocks.
@@ -686,8 +662,6 @@ xfs_alloc_ag_vextent(
         xfs_alloc_arg_t *args)  /* argument structure for allocation */
 {
         int             error=0;
-        xfs_extlen_t    reservation;
-        xfs_extlen_t    oldmax;
 
         ASSERT(args->minlen > 0);
         ASSERT(args->maxlen > 0);
@@ -696,20 +670,6 @@ xfs_alloc_ag_vextent(
         ASSERT(args->alignment > 0);
 
         /*
-         * Clamp maxlen to the amount of free space minus any reservations
-         * that have been made.
-         */
-        oldmax = args->maxlen;
-        reservation = xfs_ag_resv_needed(args->pag, args->resv);
-        if (args->maxlen > args->pag->pagf_freeblks - reservation)
-                args->maxlen = args->pag->pagf_freeblks - reservation;
-        if (args->maxlen == 0) {
-                args->agbno = NULLAGBLOCK;
-                args->maxlen = oldmax;
-                return 0;
-        }
-
-        /*
          * Branch to correct routine based on the type.
          */
         args->wasfromfl = 0;
@@ -728,8 +688,6 @@ xfs_alloc_ag_vextent(
                 /* NOTREACHED */
         }
 
-        args->maxlen = oldmax;
-
         if (error || args->agbno == NULLAGBLOCK)
                 return error;
 
@@ -838,9 +796,6 @@ xfs_alloc_ag_vextent_exact(
         args->len = XFS_AGBLOCK_MIN(tend, args->agbno + args->maxlen)
                                                 - args->agbno;
         xfs_alloc_fix_len(args);
-        if (!xfs_alloc_fix_minleft(args))
-                goto not_found;
-
         ASSERT(args->agbno + args->len <= tend);
 
         /*
@@ -1146,12 +1101,7 @@ restart:
                 XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
                 ASSERT(ltbno + ltlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
                 args->len = blen;
-                if (!xfs_alloc_fix_minleft(args)) {
-                        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
-                        trace_xfs_alloc_near_nominleft(args);
-                        return 0;
-                }
-                blen = args->len;
+
                 /*
                  * We are allocating starting at bnew for blen blocks.
                  */
@@ -1343,12 +1293,6 @@ restart:
          */
         args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
         xfs_alloc_fix_len(args);
-        if (!xfs_alloc_fix_minleft(args)) {
-                trace_xfs_alloc_near_nominleft(args);
-                xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
-                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
-                return 0;
-        }
         rlen = args->len;
         (void)xfs_alloc_compute_diff(args->agbno, rlen, args->alignment,
                                      args->datatype, ltbnoa, ltlena, &ltnew);
@@ -1550,8 +1494,6 @@ restart:
         }
         xfs_alloc_fix_len(args);
 
-        if (!xfs_alloc_fix_minleft(args))
-                goto out_nominleft;
         rlen = args->len;
         XFS_WANT_CORRUPTED_GOTO(args->mp, rlen <= flen, error0);
         /*
@@ -2070,10 +2012,20 @@ xfs_alloc_space_available(
 
         /* do we have enough free space remaining for the allocation? */
         available = (int)(pag->pagf_freeblks + pag->pagf_flcount -
-                          reservation - min_free - args->total);
-        if (available < (int)args->minleft || available <= 0)
+                          reservation - min_free - args->minleft);
+        if (available < (int)args->total)
                 return false;
 
+        /*
+         * Clamp maxlen to the amount of free space available for the actual
+         * extent allocation.
+         */
+        if (available < (int)args->maxlen && !(flags & XFS_ALLOC_FLAG_CHECK)) {
+                args->maxlen = available;
+                ASSERT(args->maxlen > 0);
+                ASSERT(args->maxlen >= args->minlen);
+        }
+
         return true;
 }
 
@@ -2119,7 +2071,8 @@ xfs_alloc_fix_freelist(
         }
 
         need = xfs_alloc_min_freelist(mp, pag);
-        if (!xfs_alloc_space_available(args, need, flags))
+        if (!xfs_alloc_space_available(args, need, flags |
+                        XFS_ALLOC_FLAG_CHECK))
                 goto out_agbp_relse;
 
         /*
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index 7c404a6b0ae3..1d0f48a501a3 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -56,7 +56,7 @@ typedef unsigned int xfs_alloctype_t;
 #define XFS_ALLOC_FLAG_FREEING  0x00000002  /* indicate caller is freeing extents*/
 #define XFS_ALLOC_FLAG_NORMAP   0x00000004  /* don't modify the rmapbt */
 #define XFS_ALLOC_FLAG_NOSHRINK 0x00000008  /* don't shrink the freelist */
-
+#define XFS_ALLOC_FLAG_CHECK    0x00000010  /* test only, don't modify args */
 
 /*
  * Argument structure for xfs_alloc routines.