[XFS] Fix block reservation mechanism.

[linux-drm-fsl-dcu.git] / fs / xfs / xfs_fsops.c

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index c064e72ada9e2beaa32f5d7d43525901de91efa0..bfde9e6d67e616b5419bd1bef389ddc569f1a537 100644 (file)
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -460,7 +460,7 @@ xfs_fs_counts(
 {
        unsigned long   s;
 
-       xfs_icsb_sync_counters_lazy(mp);
+       xfs_icsb_sync_counters_flags(mp, XFS_ICSB_LAZY_COUNT);
        s = XFS_SB_LOCK(mp);
        cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
        cnt->freertx = mp->m_sb.sb_frextents;
@@ -491,7 +491,7 @@ xfs_reserve_blocks(
        __uint64_t              *inval,
        xfs_fsop_resblks_t      *outval)
 {
-       __int64_t               lcounter, delta;
+       __int64_t               lcounter, delta, fdblks_delta;
        __uint64_t              request;
        unsigned long           s;
 
@@ -504,17 +504,35 @@ xfs_reserve_blocks(
        }
 
        request = *inval;
+
+       /*
+        * With per-cpu counters, this becomes an interesting
+        * problem. we needto work out if we are freeing or allocation
+        * blocks first, then we can do the modification as necessary.
+        *
+        * We do this under the XFS_SB_LOCK so that if we are near
+        * ENOSPC, we will hold out any changes while we work out
+        * what to do. This means that the amount of free space can
+        * change while we do this, so we need to retry if we end up
+        * trying to reserve more space than is available.
+        *
+        * We also use the xfs_mod_incore_sb() interface so that we
+        * don't have to care about whether per cpu counter are
+        * enabled, disabled or even compiled in....
+        */
+retry:
        s = XFS_SB_LOCK(mp);
+       xfs_icsb_sync_counters_flags(mp, XFS_ICSB_SB_LOCKED);
 
        /*
         * If our previous reservation was larger than the current value,
         * then move any unused blocks back to the free pool.
         */
-
+       fdblks_delta = 0;
        if (mp->m_resblks > request) {
                lcounter = mp->m_resblks_avail - request;
                if (lcounter  > 0) {            /* release unused blocks */
-                       mp->m_sb.sb_fdblocks += lcounter;
+                       fdblks_delta = lcounter;
                        mp->m_resblks_avail -= lcounter;
                }
                mp->m_resblks = request;
@@ -522,24 +540,50 @@ xfs_reserve_blocks(
                __int64_t       free;
 
                free =  mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
+               if (!free)
+                       goto out; /* ENOSPC and fdblks_delta = 0 */
+
                delta = request - mp->m_resblks;
                lcounter = free - delta;
                if (lcounter < 0) {
                        /* We can't satisfy the request, just get what we can */
                        mp->m_resblks += free;
                        mp->m_resblks_avail += free;
+                       fdblks_delta = -free;
                        mp->m_sb.sb_fdblocks = XFS_ALLOC_SET_ASIDE(mp);
                } else {
+                       fdblks_delta = -delta;
                        mp->m_sb.sb_fdblocks =
                                lcounter + XFS_ALLOC_SET_ASIDE(mp);
                        mp->m_resblks = request;
                        mp->m_resblks_avail += delta;
                }
        }
-
+out:
        outval->resblks = mp->m_resblks;
        outval->resblks_avail = mp->m_resblks_avail;
        XFS_SB_UNLOCK(mp, s);
+
+       if (fdblks_delta) {
+               /*
+                * If we are putting blocks back here, m_resblks_avail is
+                * already at it's max so this will put it in the free pool.
+                *
+                * If we need space, we'll either succeed in getting it
+                * from the free block count or we'll get an enospc. If
+                * we get a ENOSPC, it means things changed while we were
+                * calculating fdblks_delta and so we should try again to
+                * see if there is anything left to reserve.
+                *
+                * Don't set the reserved flag here - we don't want to reserve
+                * the extra reserve blocks from the reserve.....
+                */
+               int error;
+               error = xfs_mod_incore_sb(mp, XFS_SBS_FDBLOCKS, fdblks_delta, 0);
+               if (error == ENOSPC)
+                       goto retry;
+       }
+
        return 0;
 }