OCFS2: Allow huge (> 16 TiB) volumes to mount

The OCFS2 developers have already done all of the hard work to allow
volumes larger than 16 TiB.  But there is still a "sanity check" in
fs/ocfs2/super.c that prevents the mounting of such volumes, even when
the cluster size and journal options would allow it.

This patch replaces that sanity check with a more sophisticated one to
mount a huge volume provided that (a) it is addressable by the raw
word/address size of the system (borrowing a test from ext4); (b) the
volume is using JBD2; and (c) the JBD2_FEATURE_INCOMPAT_64BIT flag is
set on the journal.

I factored out the sanity check into its own function.  I also moved it
from ocfs2_initialize_super() down to ocfs2_check_volume(); any earlier,
and the journal will not have been initialized yet.

This patch is one of a pair, and it depends on the other ("JBD2: Allow
feature checks before journal recovery").

I have tested this patch on small volumes, huge volumes, and huge
volumes without 64-bit block support in the journal.  All of them appear
to work or to fail gracefully, as appropriate.

Signed-off-by: Patrick LoPresti <lopresti@gmail.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index fa1be1b..4741539 100644 (file)
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -1990,6 +1990,36 @@ static int ocfs2_setup_osb_uuid(struct ocfs2_super *osb, const unsigned char *uu
        return 0;
 }
 
+/* Make sure entire volume is addressable by our journal.  Requires
+   osb_clusters_at_boot to be valid and for the journal to have been
+   initialized by ocfs2_journal_init(). */
+static int ocfs2_journal_addressable(struct ocfs2_super *osb)
+{
+       int status = 0;
+       u64 max_block =
+               ocfs2_clusters_to_blocks(osb->sb,
+                                        osb->osb_clusters_at_boot) - 1;
+
+       /* 32-bit block number is always OK. */
+       if (max_block <= (u32)~0ULL)
+               goto out;
+
+       /* Volume is "huge", so see if our journal is new enough to
+          support it. */
+       if (!(OCFS2_HAS_COMPAT_FEATURE(osb->sb,
+                                      OCFS2_FEATURE_COMPAT_JBD2_SB) &&
+             jbd2_journal_check_used_features(osb->journal->j_journal, 0, 0,
+                                              JBD2_FEATURE_INCOMPAT_64BIT))) {
+               mlog(ML_ERROR, "The journal cannot address the entire volume. "
+                    "Enable the 'block64' journal option with tunefs.ocfs2");
+               status = -EFBIG;
+               goto out;
+       }
+
+ out:
+       return status;
+}
+
 static int ocfs2_initialize_super(struct super_block *sb,
                                  struct buffer_head *bh,
                                  int sector_size,
@@ -2002,6 +2032,7 @@ static int ocfs2_initialize_super(struct super_block *sb,
        struct ocfs2_journal *journal;
        __le32 uuid_net_key;
        struct ocfs2_super *osb;
+       u64 total_blocks;
 
        mlog_entry_void();
 
@@ -2214,11 +2245,15 @@ static int ocfs2_initialize_super(struct super_block *sb,
                goto bail;
        }
 
-       if (ocfs2_clusters_to_blocks(osb->sb, le32_to_cpu(di->i_clusters) - 1)
-           > (u32)~0UL) {
-               mlog(ML_ERROR, "Volume might try to write to blocks beyond "
-                    "what jbd can address in 32 bits.\n");
-               status = -EINVAL;
+       total_blocks = ocfs2_clusters_to_blocks(osb->sb,
+                                               le32_to_cpu(di->i_clusters));
+
+       status = generic_check_addressable(osb->sb->s_blocksize_bits,
+                                          total_blocks);
+       if (status) {
+               mlog(ML_ERROR, "Volume too large "
+                    "to mount safely on this system");
+               status = -EFBIG;
                goto bail;
        }
 
@@ -2380,6 +2415,12 @@ static int ocfs2_check_volume(struct ocfs2_super *osb)
                goto finally;
        }
 
+       /* Now that journal has been initialized, check to make sure
+          entire volume is addressable. */
+       status = ocfs2_journal_addressable(osb);
+       if (status)
+               goto finally;
+
        /* If the journal was unmounted cleanly then we don't want to
         * recover anything. Otherwise, journal_load will do that
         * dirty work for us :) */