xfs: fix up inode32/64 (re)mount handling

inode32/inode64 allocator behavior with respect to mount, remount
and growfs is a little tricky.

The inode32 mount option should only enable the inode32 allocator
heuristics if the filesystem is large enough for 64-bit inodes to
exist.  Today, it has this behavior on the initial mount, but a
remount with inode32 unconditionally changes the allocation
heuristics, even for a small fs.

Also, an inode32 mounted small filesystem should transition to the
inode32 allocator if the filesystem is subsequently grown to a
sufficient size.  Today that does not happen.

This patch consolidates xfs_set_inode32 and xfs_set_inode64 into a
single new function, and moves the "is the maximum inode number big
enough to matter" test into that function, so it doesn't rely on the
caller to get it right - which remount did not do, previously.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

4 files changed, 60 insertions, 71 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index bb753b359bee..a773ef33f559 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -185,9 +185,6 @@ xfs_initialize_perag(
         xfs_agnumber_t  index;
         xfs_agnumber_t  first_initialised = 0;
         xfs_perag_t     *pag;
-        xfs_agino_t     agino;
-        xfs_ino_t       ino;
-        xfs_sb_t        *sbp = &mp->m_sb;
         int             error = -ENOMEM;
 
         /*
@@ -230,22 +227,7 @@ xfs_initialize_perag(
                 radix_tree_preload_end();
         }
 
-        /*
-         * If we mount with the inode64 option, or no inode overflows
-         * the legacy 32-bit address space clear the inode32 option.
-         */
-        agino = XFS_OFFBNO_TO_AGINO(mp, sbp->sb_agblocks - 1, 0);
-        ino = XFS_AGINO_TO_INO(mp, agcount - 1, agino);
-
-        if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) && ino > XFS_MAXINUMBER_32)
-                mp->m_flags |= XFS_MOUNT_32BITINODES;
-        else
-                mp->m_flags &= ~XFS_MOUNT_32BITINODES;
-
-        if (mp->m_flags & XFS_MOUNT_32BITINODES)
-                index = xfs_set_inode32(mp, agcount);
-        else
-                index = xfs_set_inode64(mp, agcount);
+        index = xfs_set_inode_alloc(mp, agcount);
 
         if (maxagi)
                 *maxagi = index;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index b57098481c10..af01458def6a 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -166,9 +166,8 @@ typedef struct xfs_mount {
 #define XFS_MOUNT_GRPID         (1ULL << 9)     /* group-ID assigned from directory */
 #define XFS_MOUNT_NORECOVERY    (1ULL << 10)    /* no recovery - dirty fs */
 #define XFS_MOUNT_DFLT_IOSIZE   (1ULL << 12)    /* set default i/o size */
-#define XFS_MOUNT_32BITINODES   (1ULL << 14)    /* do not create inodes above
-                                                 * 32 bits in size */
-#define XFS_MOUNT_SMALL_INUMS   (1ULL << 15)    /* users wants 32bit inodes */
+#define XFS_MOUNT_SMALL_INUMS   (1ULL << 14)    /* user wants 32bit inodes */
+#define XFS_MOUNT_32BITINODES   (1ULL << 15)    /* inode32 allocator active */
 #define XFS_MOUNT_NOUUID        (1ULL << 16)    /* ignore uuid during mount */
 #define XFS_MOUNT_BARRIER       (1ULL << 17)
 #define XFS_MOUNT_IKEEP         (1ULL << 18)    /* keep empty inode clusters*/
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 8dd7d165902d..d85087bc0c40 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -580,23 +580,35 @@ xfs_max_file_offset(
 }
 
 /*
- * xfs_set_inode32() and xfs_set_inode64() are passed an agcount
- * because in the growfs case, mp->m_sb.sb_agcount is not updated
- * yet to the potentially higher ag count.
+ * Set parameters for inode allocation heuristics, taking into account
+ * filesystem size and inode32/inode64 mount options; i.e. specifically
+ * whether or not XFS_MOUNT_SMALL_INUMS is set.
+ *
+ * Inode allocation patterns are altered only if inode32 is requested
+ * (XFS_MOUNT_SMALL_INUMS), and the filesystem is sufficiently large.
+ * If altered, XFS_MOUNT_32BITINODES is set as well.
+ *
+ * An agcount independent of that in the mount structure is provided
+ * because in the growfs case, mp->m_sb.sb_agcount is not yet updated
+ * to the potentially higher ag count.
+ *
+ * Returns the maximum AG index which may contain inodes.
  */
 xfs_agnumber_t
-xfs_set_inode32(struct xfs_mount *mp, xfs_agnumber_t agcount)
+xfs_set_inode_alloc(
+        struct xfs_mount *mp,
+        xfs_agnumber_t  agcount)
 {
-        xfs_agnumber_t  index = 0;
+        xfs_agnumber_t  index;
         xfs_agnumber_t  maxagi = 0;
         xfs_sb_t        *sbp = &mp->m_sb;
         xfs_agnumber_t  max_metadata;
         xfs_agino_t     agino;
         xfs_ino_t       ino;
-        xfs_perag_t     *pag;
 
-        /* Calculate how much should be reserved for inodes to meet
-         * the max inode percentage.
+        /*
+         * Calculate how much should be reserved for inodes to meet
+         * the max inode percentage.  Used only for inode32.
          */
         if (mp->m_maxicount) {
                 __uint64_t      icount;
@@ -610,54 +622,48 @@ xfs_set_inode32(struct xfs_mount *mp, xfs_agnumber_t agcount)
                 max_metadata = agcount;
         }
 
+        /* Get the last possible inode in the filesystem */
         agino = XFS_OFFBNO_TO_AGINO(mp, sbp->sb_agblocks - 1, 0);
+        ino = XFS_AGINO_TO_INO(mp, agcount - 1, agino);
+
+        /*
+         * If user asked for no more than 32-bit inodes, and the fs is
+         * sufficiently large, set XFS_MOUNT_32BITINODES if we must alter
+         * the allocator to accommodate the request.
+         */
+        if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) && ino > XFS_MAXINUMBER_32)
+                mp->m_flags |= XFS_MOUNT_32BITINODES;
+        else
+                mp->m_flags &= ~XFS_MOUNT_32BITINODES;
 
         for (index = 0; index < agcount; index++) {
-                ino = XFS_AGINO_TO_INO(mp, index, agino);
+                struct xfs_perag        *pag;
 
-                if (ino > XFS_MAXINUMBER_32) {
-                        pag = xfs_perag_get(mp, index);
-                        pag->pagi_inodeok = 0;
-                        pag->pagf_metadata = 0;
-                        xfs_perag_put(pag);
-                        continue;
-                }
+                ino = XFS_AGINO_TO_INO(mp, index, agino);
 
                 pag = xfs_perag_get(mp, index);
-                pag->pagi_inodeok = 1;
-                maxagi++;
-                if (index < max_metadata)
-                        pag->pagf_metadata = 1;
-                xfs_perag_put(pag);
-        }
-        mp->m_flags |= (XFS_MOUNT_32BITINODES |
-                        XFS_MOUNT_SMALL_INUMS);
 
-        return maxagi;
-}
-
-xfs_agnumber_t
-xfs_set_inode64(struct xfs_mount *mp, xfs_agnumber_t agcount)
-{
-        xfs_agnumber_t index = 0;
-
-        for (index = 0; index < agcount; index++) {
-                struct xfs_perag        *pag;
+                if (mp->m_flags & XFS_MOUNT_32BITINODES) {
+                        if (ino > XFS_MAXINUMBER_32) {
+                                pag->pagi_inodeok = 0;
+                                pag->pagf_metadata = 0;
+                        } else {
+                                pag->pagi_inodeok = 1;
+                                maxagi++;
+                                if (index < max_metadata)
+                                        pag->pagf_metadata = 1;
+                                else
+                                        pag->pagf_metadata = 0;
+                        }
+                } else {
+                        pag->pagi_inodeok = 1;
+                        pag->pagf_metadata = 0;
+                }
 
-                pag = xfs_perag_get(mp, index);
-                pag->pagi_inodeok = 1;
-                pag->pagf_metadata = 0;
                 xfs_perag_put(pag);
         }
 
-        /* There is no need for lock protection on m_flags,
-         * the rw_semaphore of the VFS superblock is locked
-         * during mount/umount/remount operations, so this is
-         * enough to avoid concurency on the m_flags field
-         */
-        mp->m_flags &= ~(XFS_MOUNT_32BITINODES |
-                         XFS_MOUNT_SMALL_INUMS);
-        return index;
+        return (mp->m_flags & XFS_MOUNT_32BITINODES) ? maxagi : agcount;
 }
 
 STATIC int
@@ -1227,10 +1233,12 @@ xfs_fs_remount(
                         mp->m_flags &= ~XFS_MOUNT_BARRIER;
                         break;
                 case Opt_inode64:
-                        mp->m_maxagi = xfs_set_inode64(mp, sbp->sb_agcount);
+                        mp->m_flags &= ~XFS_MOUNT_SMALL_INUMS;
+                        mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
                         break;
                 case Opt_inode32:
-                        mp->m_maxagi = xfs_set_inode32(mp, sbp->sb_agcount);
+                        mp->m_flags |= XFS_MOUNT_SMALL_INUMS;
+                        mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
                         break;
                 default:
                         /*
diff --git a/fs/xfs/xfs_super.h b/fs/xfs/xfs_super.h
index 499058fea303..2dfb1ce4585f 100644
--- a/fs/xfs/xfs_super.h
+++ b/fs/xfs/xfs_super.h
@@ -65,8 +65,8 @@ extern __uint64_t xfs_max_file_offset(unsigned int);
 
 extern void xfs_flush_inodes(struct xfs_mount *mp);
 extern void xfs_blkdev_issue_flush(struct xfs_buftarg *);
-extern xfs_agnumber_t xfs_set_inode32(struct xfs_mount *, xfs_agnumber_t agcount);
-extern xfs_agnumber_t xfs_set_inode64(struct xfs_mount *, xfs_agnumber_t agcount);
+extern xfs_agnumber_t xfs_set_inode_alloc(struct xfs_mount *,
+                                           xfs_agnumber_t agcount);
 
 extern const struct export_operations xfs_export_operations;
 extern const struct xattr_handler *xfs_xattr_handlers[];