ocfs2: lighten up allocate transaction

The issue scenario is as following:

When fallocating a very large disk space for a small file,
__ocfs2_extend_allocation attempts to get a very large transaction.  For
some journal sizes, there may be not enough room for this transaction,
and the fallocate will fail.

The patch below extends & restarts the transaction as necessary while
allocating space, and should work with even the smallest journal.  This
patch refers ext4 resize.

Test:
# mkfs.ocfs2 -b 4K -C 32K -T datafiles /dev/sdc
...(jounral size is 32M)
# mount.ocfs2 /dev/sdc /mnt/ocfs2/
# touch /mnt/ocfs2/1.log
# fallocate -o 0 -l 400G /mnt/ocfs2/1.log
fallocate: /mnt/ocfs2/1.log: fallocate failed: Cannot allocate memory
# tail -f /var/log/messages
[ 7372.278591] JBD: fallocate wants too many credits (2051 > 2048)
[ 7372.278597] (fallocate,6438,0):__ocfs2_extend_allocation:709 ERROR: status = -12
[ 7372.278603] (fallocate,6438,0):ocfs2_allocate_unwritten_extents:1504 ERROR: status = -12
[ 7372.278607] (fallocate,6438,0):__ocfs2_change_file_space:1955 ERROR: status = -12
^C
With this patch, the test works well.

Signed-off-by: Younger Liu <younger.liu@huawei.com>
Cc: Jie Liu <jeff.liu@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index 242170d83971..a126cb37ca4d 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -455,6 +455,41 @@ bail:
         return status;
 }
 
+/*
+ * If we have fewer than thresh credits, extend by OCFS2_MAX_TRANS_DATA.
+ * If that fails, restart the transaction & regain write access for the
+ * buffer head which is used for metadata modifications.
+ * Taken from Ext4: extend_or_restart_transaction()
+ */
+int ocfs2_allocate_extend_trans(handle_t *handle, int thresh)
+{
+        int status, old_nblks;
+
+        BUG_ON(!handle);
+
+        old_nblks = handle->h_buffer_credits;
+        trace_ocfs2_allocate_extend_trans(old_nblks, thresh);
+
+        if (old_nblks < thresh)
+                return 0;
+
+        status = jbd2_journal_extend(handle, OCFS2_MAX_TRANS_DATA);
+        if (status < 0) {
+                mlog_errno(status);
+                goto bail;
+        }
+
+        if (status > 0) {
+                status = jbd2_journal_restart(handle, OCFS2_MAX_TRANS_DATA);
+                if (status < 0)
+                        mlog_errno(status);
+        }
+
+bail:
+        return status;
+}
+
+
 struct ocfs2_triggers {
         struct jbd2_buffer_trigger_type ot_triggers;
         int                             ot_offset;