4 files changed, 40 insertions, 31 deletions

diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h
index 650591f999ae..5a4256120ccc 100644
--- a/fs/xfs/xfs_alloc.h
+++ b/fs/xfs/xfs_alloc.h
@@ -44,6 +44,26 @@ typedef enum xfs_alloctype
 #define XFS_ALLOC_FLAG_FREEING  0x00000002  /* indicate caller is freeing extents*/
 
 /*
+ * In order to avoid ENOSPC-related deadlock caused by
+ * out-of-order locking of AGF buffer (PV 947395), we place
+ * constraints on the relationship among actual allocations for
+ * data blocks, freelist blocks, and potential file data bmap
+ * btree blocks. However, these restrictions may result in no
+ * actual space allocated for a delayed extent, for example, a data
+ * block in a certain AG is allocated but there is no additional
+ * block for the additional bmap btree block due to a split of the
+ * bmap btree of the file. The result of this may lead to an
+ * infinite loop in xfssyncd when the file gets flushed to disk and
+ * all delayed extents need to be actually allocated. To get around
+ * this, we explicitly set aside a few blocks which will not be
+ * reserved in delayed allocation. Considering the minimum number of
+ * needed freelist blocks is 4 fsbs _per AG_, a potential split of file's bmap
+ * btree requires 1 fsb, so we set the number of set-aside blocks
+ * to 4 + 4*agcount.
+ */
+#define XFS_ALLOC_SET_ASIDE(mp)  (4 + ((mp)->m_sb.sb_agcount * 4))
+
+/*
  * Argument structure for xfs_alloc routines.
  * This is turned into a structure to avoid having 20 arguments passed
  * down several levels of the stack.
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 077629bab532..c064e72ada9e 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -462,7 +462,7 @@ xfs_fs_counts(
 
         xfs_icsb_sync_counters_lazy(mp);
         s = XFS_SB_LOCK(mp);
-        cnt->freedata = mp->m_sb.sb_fdblocks;
+        cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
         cnt->freertx = mp->m_sb.sb_frextents;
         cnt->freeino = mp->m_sb.sb_ifree;
         cnt->allocino = mp->m_sb.sb_icount;
@@ -519,15 +519,19 @@ xfs_reserve_blocks(
                 }
                 mp->m_resblks = request;
         } else {
+                __int64_t       free;
+
+                free =  mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
                 delta = request - mp->m_resblks;
-                lcounter = mp->m_sb.sb_fdblocks - delta;
+                lcounter = free - delta;
                 if (lcounter < 0) {
                         /* We can't satisfy the request, just get what we can */
-                        mp->m_resblks += mp->m_sb.sb_fdblocks;
-                        mp->m_resblks_avail += mp->m_sb.sb_fdblocks;
-                        mp->m_sb.sb_fdblocks = 0;
+                        mp->m_resblks += free;
+                        mp->m_resblks_avail += free;
+                        mp->m_sb.sb_fdblocks = XFS_ALLOC_SET_ASIDE(mp);
                 } else {
-                        mp->m_sb.sb_fdblocks = lcounter;
+                        mp->m_sb.sb_fdblocks =
+                                lcounter + XFS_ALLOC_SET_ASIDE(mp);
                         mp->m_resblks = request;
                         mp->m_resblks_avail += delta;
                 }
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 4be5c0b2d296..9dfae18d995f 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1243,24 +1243,6 @@ xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
         xfs_trans_log_buf(tp, bp, first, last);
 }
 
-/*
- * In order to avoid ENOSPC-related deadlock caused by
- * out-of-order locking of AGF buffer (PV 947395), we place
- * constraints on the relationship among actual allocations for
- * data blocks, freelist blocks, and potential file data bmap
- * btree blocks. However, these restrictions may result in no
- * actual space allocated for a delayed extent, for example, a data
- * block in a certain AG is allocated but there is no additional
- * block for the additional bmap btree block due to a split of the
- * bmap btree of the file. The result of this may lead to an
- * infinite loop in xfssyncd when the file gets flushed to disk and
- * all delayed extents need to be actually allocated. To get around
- * this, we explicitly set aside a few blocks which will not be
- * reserved in delayed allocation. Considering the minimum number of
- * needed freelist blocks is 4 fsbs, a potential split of file's bmap
- * btree requires 1 fsb, so we set the number of set-aside blocks to 8.
-*/
-#define SET_ASIDE_BLOCKS 8
 
 /*
  * xfs_mod_incore_sb_unlocked() is a utility routine common used to apply
@@ -1306,7 +1288,8 @@ xfs_mod_incore_sb_unlocked(xfs_mount_t *mp, xfs_sb_field_t field,
                 return 0;
         case XFS_SBS_FDBLOCKS:
 
-                lcounter = (long long)mp->m_sb.sb_fdblocks - SET_ASIDE_BLOCKS;
+                lcounter = (long long)
+                        mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
                 res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);
 
                 if (delta > 0) {                /* Putting blocks back */
@@ -1340,7 +1323,7 @@ xfs_mod_incore_sb_unlocked(xfs_mount_t *mp, xfs_sb_field_t field,
                         }
                 }
 
-                mp->m_sb.sb_fdblocks = lcounter + SET_ASIDE_BLOCKS;
+                mp->m_sb.sb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
                 return 0;
         case XFS_SBS_FREXTENTS:
                 lcounter = (long long)mp->m_sb.sb_frextents;
@@ -2021,7 +2004,8 @@ xfs_icsb_sync_counters_lazy(
  * when we get near ENOSPC.
  */
 #define XFS_ICSB_INO_CNTR_REENABLE      64
-#define XFS_ICSB_FDBLK_CNTR_REENABLE    512
+#define XFS_ICSB_FDBLK_CNTR_REENABLE(mp) \
+                (512 + XFS_ALLOC_SET_ASIDE(mp))
 STATIC void
 xfs_icsb_balance_counter(
         xfs_mount_t     *mp,
@@ -2055,7 +2039,7 @@ xfs_icsb_balance_counter(
         case XFS_SBS_FDBLOCKS:
                 count = mp->m_sb.sb_fdblocks;
                 resid = do_div(count, weight);
-                if (count < XFS_ICSB_FDBLK_CNTR_REENABLE)
+                if (count < XFS_ICSB_FDBLK_CNTR_REENABLE(mp))
                         goto out;
                 break;
         default:
@@ -2110,11 +2094,11 @@ again:
         case XFS_SBS_FDBLOCKS:
                 BUG_ON((mp->m_resblks - mp->m_resblks_avail) != 0);
 
-                lcounter = icsbp->icsb_fdblocks;
+                lcounter = icsbp->icsb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
                 lcounter += delta;
                 if (unlikely(lcounter < 0))
                         goto slow_path;
-                icsbp->icsb_fdblocks = lcounter;
+                icsbp->icsb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
                 break;
         default:
                 BUG();
diff --git a/fs/xfs/xfs_vfsops.c b/fs/xfs/xfs_vfsops.c
index b427d220a169..a34796e57afb 100644
--- a/fs/xfs/xfs_vfsops.c
+++ b/fs/xfs/xfs_vfsops.c
@@ -811,7 +811,8 @@ xfs_statvfs(
         statp->f_bsize = sbp->sb_blocksize;
         lsize = sbp->sb_logstart ? sbp->sb_logblocks : 0;
         statp->f_blocks = sbp->sb_dblocks - lsize;
-        statp->f_bfree = statp->f_bavail = sbp->sb_fdblocks;
+        statp->f_bfree = statp->f_bavail =
+                                sbp->sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
         fakeinos = statp->f_bfree << sbp->sb_inopblog;
 #if XFS_BIG_INUMS
         fakeinos += mp->m_inoadd;