xfs: embed the xlog_op_header in the unmount record

Remove another case where xlog_write() has to prepend an opheader to
a log transaction. The unmount record + ophdr is smaller than the
minimum amount of space guaranteed to be free in an iclog (2 *
sizeof(ophdr)) and so we don't have to care about an unmount record
being split across 2 iclogs.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index f6fa5426278bf6a3e6a57ac16cb444f37ddd256c..00e9af9b246a40496186c066d3c8b0a9ca272868 100644 (file)
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -901,12 +901,22 @@ xlog_write_unmount_record(
        struct xlog             *log,
        struct xlog_ticket      *ticket)
 {
-       struct xfs_unmount_log_format ulf = {
-               .magic = XLOG_UNMOUNT_TYPE,
+       struct  {
+               struct xlog_op_header ophdr;
+               struct xfs_unmount_log_format ulf;
+       } unmount_rec = {
+               .ophdr = {
+                       .oh_clientid = XFS_LOG,
+                       .oh_tid = cpu_to_be32(ticket->t_tid),
+                       .oh_flags = XLOG_UNMOUNT_TRANS,
+               },
+               .ulf = {
+                       .magic = XLOG_UNMOUNT_TYPE,
+               },
        };
        struct xfs_log_iovec reg = {
-               .i_addr = &ulf,
-               .i_len = sizeof(ulf),
+               .i_addr = &unmount_rec,
+               .i_len = sizeof(unmount_rec),
                .i_type = XLOG_REG_TYPE_UNMOUNT,
        };
        struct xfs_log_vec vec = {
@@ -914,8 +924,12 @@ xlog_write_unmount_record(
                .lv_iovecp = &reg,
        };
 
+       BUILD_BUG_ON((sizeof(struct xlog_op_header) +
+                     sizeof(struct xfs_unmount_log_format)) !=
+                                                       sizeof(unmount_rec));
+
        /* account for space used by record data */
-       ticket->t_curr_res -= sizeof(ulf);
+       ticket->t_curr_res -= sizeof(unmount_rec);
 
        return xlog_write(log, NULL, &vec, ticket, XLOG_UNMOUNT_TRANS);
 }
@@ -2253,6 +2267,8 @@ xlog_write_calc_vec_length(
 
        /* Don't account for regions with embedded ophdrs */
        if (optype && headers > 0) {
+               if (optype & XLOG_UNMOUNT_TRANS)
+                       headers--;
                if (optype & XLOG_START_TRANS) {
                        ASSERT(headers >= 2);
                        headers -= 2;
@@ -2458,12 +2474,11 @@ xlog_write(
 
        /*
         * If this is a commit or unmount transaction, we don't need a start
-        * record to be written.  We do, however, have to account for the
-        * commit or unmount header that gets written. Hence we always have
-        * to account for an extra xlog_op_header here for commit and unmount
-        * records.
+        * record to be written.  We do, however, have to account for the commit
+        * header that gets written. Hence we always have to account for an
+        * extra xlog_op_header here for commit records.
         */
-       if (optype & (XLOG_COMMIT_TRANS | XLOG_UNMOUNT_TRANS))
+       if (optype & XLOG_COMMIT_TRANS)
                ticket->t_curr_res -= sizeof(struct xlog_op_header);
        if (ticket->t_curr_res < 0) {
                xfs_alert_tag(log->l_mp, XFS_PTAG_LOGRES,
@@ -2527,6 +2542,8 @@ xlog_write(
                                ophdr = reg->i_addr;
                                if (index)
                                        optype &= ~XLOG_START_TRANS;
+                       } else if (optype & XLOG_UNMOUNT_TRANS) {
+                               ophdr = reg->i_addr;
                        } else {
                                ophdr = xlog_write_setup_ophdr(log, ptr,
                                                        ticket, optype);
@@ -2557,7 +2574,7 @@ xlog_write(
                        /*
                         * Copy region.
                         *
-                        * Commit and unmount records just log an opheader, so
+                        * Commit records just log an opheader, so
                         * we can have empty payloads with no data region to
                         * copy.  Hence we only copy the payload if the vector
                         * says it has data to copy.