[PATCH 21/45] xfs: embed the xlog_op_header in the unmount record

Dave Chinner
2021-03-05T05:12:29Z

From: Dave Chinner <dchinner@redhat.com>

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>
---
fs/xfs/xfs_log.c | 35 ++++++++++++++++++++++++-----------
1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index b2f9fb1b4fed..94711b9ff007 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -798,12 +798,22 @@ 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 = {
@@ -812,7 +822,7 @@ xlog_write_unmount_record(
};

/* account for space used by record data */
- ticket->t_curr_res -= sizeof(ulf);
+ ticket->t_curr_res -= sizeof(unmount_rec);

/*
* For external log devices, we need to flush the data device cache
@@ -2138,6 +2148,8 @@ 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;
@@ -2352,12 +2364,11 @@ 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,
@@ -2428,6 +2439,8 @@ 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);
@@ -2458,7 +2471,7 @@ 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.
--
2.28.0