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Subject[PATCH 2/2] OCFS2: Allow huge (> 16 TiB) volumes to mount
Date
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>


diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 0eaa929..b809508 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -1991,6 +1991,47 @@ static int ocfs2_setup_osb_uuid(struct ocfs2_super *osb, const unsigned char *uu
return 0;
}

+/* Check to make sure entire volume is addressable on this system.
+ Requires osb_clusters_at_boot to be valid and for the journal to
+ have been initialized by ocfs2_journal_init(). */
+static int ocfs2_check_addressable(struct ocfs2_super *osb)
+{
+ int status = 0;
+ u64 max_block =
+ ocfs2_clusters_to_blocks(osb->sb,
+ osb->osb_clusters_at_boot) - 1;
+
+ /* Absolute addressability check (borrowed from ext4/super.c) */
+ if ((max_block >
+ (sector_t)(~0LL) >> (osb->sb->s_blocksize_bits - 9)) ||
+ (max_block > (pgoff_t)(~0LL) >> (PAGE_CACHE_SHIFT -
+ osb->sb->s_blocksize_bits))) {
+ mlog(ML_ERROR, "Volume too large "
+ "to mount safely on this system");
+ status = -EFBIG;
+ goto out;
+ }
+
+ /* 32-bit block number is always OK. */
+ if (max_block <= (u32)~0UL)
+ 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,
@@ -2215,14 +2256,6 @@ 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;
- goto bail;
- }
-
if (ocfs2_setup_osb_uuid(osb, di->id2.i_super.s_uuid,
sizeof(di->id2.i_super.s_uuid))) {
mlog(ML_ERROR, "Out of memory trying to setup our uuid.\n");
@@ -2381,6 +2414,12 @@ 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_check_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 :) */

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