[PATCH 08/20] xfs: factor out splitting of an iclog from xlog_sync

Christoph Hellwig
2019-05-23T17:39:33Z

Split out a self-contained chunk of code from xlog_sync that calculates
the split offset for an iclog that wraps the log end and bumps the
cycles for the second half.

Use the chance to bring some sanity to the variables used to track the
split in xlog_sync by not changing the count variable, and instead use
split as the offset for the split and use those to calculate the
sizes and offsets for the two write buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/xfs_log.c | 63 +++++++++++++++++++++++++-----------------------
1 file changed, 33 insertions(+), 30 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 9a81d2d32ad9..885470f08554 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1804,6 +1804,32 @@ xlog_write_iclog(
xfs_buf_submit(bp);
}

+/*
+ * Bump the cycle numbers at the start of each block in the part of the iclog
+ * that ends up in the buffer that gets written to the start of the log.
+ *
+ * Watch out for the header magic number case, though.
+ */
+static unsigned int
+xlog_split_iclog(
+ struct xlog *log,
+ void *data,
+ uint64_t bno,
+ unsigned int count)
+{
+ unsigned int split_offset = BBTOB(log->l_logBBsize - bno), i;
+
+ for (i = split_offset; i < count; i += BBSIZE) {
+ uint32_t cycle = get_unaligned_be32(data + i);
+
+ if (++cycle == XLOG_HEADER_MAGIC_NUM)
+ cycle++;
+ put_unaligned_be32(cycle, data + i);
+ }
+
+ return split_offset;
+}
+
/*
* Flush out the in-core log (iclog) to the on-disk log in an asynchronous
* fashion. Previously, we should have moved the current iclog
@@ -1832,13 +1858,12 @@ xlog_sync(
struct xlog *log,
struct xlog_in_core *iclog)
{
- int i;
uint count; /* byte count of bwrite */
uint count_init; /* initial count before roundup */
int roundoff; /* roundoff to BB or stripe */
- int split = 0; /* split write into two regions */
int v2 = xfs_sb_version_haslogv2(&log->l_mp->m_sb);
uint64_t bno;
+ unsigned int split = 0;
int size;
bool flush = true;

@@ -1881,32 +1906,8 @@ xlog_sync(
bno = BLOCK_LSN(be64_to_cpu(iclog->ic_header.h_lsn));

/* Do we need to split this write into 2 parts? */
- if (bno + BTOBB(count) > log->l_logBBsize) {
- char *dptr;
-
- split = count - (BBTOB(log->l_logBBsize - bno));
- count = BBTOB(log->l_logBBsize - bno);
- iclog->ic_bwritecnt = 2;
-
- /*
- * Bump the cycle numbers at the start of each block in the
- * part of the iclog that ends up in the buffer that gets
- * written to the start of the log.
- *
- * Watch out for the header magic number case, though.
- */
- dptr = (char *)&iclog->ic_header + count;
- for (i = 0; i < split; i += BBSIZE) {
- uint32_t cycle = be32_to_cpu(*(__be32 *)dptr);
- if (++cycle == XLOG_HEADER_MAGIC_NUM)
- cycle++;
- *(__be32 *)dptr = cpu_to_be32(cycle);
-
- dptr += BBSIZE;
- }
- } else {
- iclog->ic_bwritecnt = 1;
- }
+ if (bno + BTOBB(count) > log->l_logBBsize)
+ split = xlog_split_iclog(log, &iclog->ic_header, bno, count);

/* calculcate the checksum */
iclog->ic_header.h_crc = xlog_cksum(log, &iclog->ic_header,
@@ -1939,14 +1940,16 @@ xlog_sync(
flush = false;
}

- iclog->ic_bp->b_io_length = BTOBB(count);
+ iclog->ic_bp->b_io_length = BTOBB(split ? split : count);
+ iclog->ic_bwritecnt = split ? 2 : 1;

xlog_verify_iclog(log, iclog, count, true);
xlog_write_iclog(log, iclog, iclog->ic_bp, bno, flush);

if (split) {
xfs_buf_associate_memory(iclog->ic_log->l_xbuf,
- (char *)&iclog->ic_header + count, split);
+ (char *)&iclog->ic_header + split,
+ count - split);
xlog_write_iclog(log, iclog, iclog->ic_log->l_xbuf, 0, false);
}
}
--
2.20.1