[PATCH 13/14] staging: lustre: llog: limit file size of plain logs

[James Simmons]

From: Alex Zhuravlev <alexey.zhuravlev@xxxxxxxxx>

on small filesystems plain log can grow dramatically. especially
given large record sizes produced by DNE and extended chunksize.
I saw >50% of space consumed by a single llog file which was still
in use. this leads to test failures (sanityn, etc).
the patch introduces additional limit on plain llog size, which
is calculated as <free space>/64 (128MB at most) at llog creation
time.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@xxxxxxxxx>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6838
Reviewed-on: https://review.whamcloud.com/18028
Reviewed-by: Andreas Dilger <andreas.dilger@xxxxxxxxx>
Reviewed-by: wangdi <di.wang@xxxxxxxxx>
Reviewed-by: Mike Pershin <mike.pershin@xxxxxxxxx>
Reviewed-by: Oleg Drokin <oleg.drokin@xxxxxxxxx>
Signed-off-by: James Simmons <jsimmons@xxxxxxxxxxxxx>
---
 drivers/staging/lustre/lustre/obdclass/llog.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/staging/lustre/lustre/obdclass/llog.c b/drivers/staging/lustre/lustre/obdclass/llog.c
index 83c5b62..320ff6b 100644
--- a/drivers/staging/lustre/lustre/obdclass/llog.c
+++ b/drivers/staging/lustre/lustre/obdclass/llog.c
@@ -319,10 +319,26 @@ static int llog_process_thread(void *arg)
 				 * the case and re-read the current chunk
 				 * otherwise.
 				 */
+				int records;
+
 				if (index > loghandle->lgh_last_idx) {
 					rc = 0;
 					goto out;
 				}
+				/* <2 records means no more records
+				 * if the last record we processed was
+				 * the final one, then the underlying
+				 * object might have been destroyed yet.
+				 * we better don't access that..
+				 */
+				mutex_lock(&loghandle->lgh_hdr_mutex);
+				records = loghandle->lgh_hdr->llh_count;
+				mutex_unlock(&loghandle->lgh_hdr_mutex);
+				if (records <= 1) {
+					rc = 0;
+					goto out;
+				}
+
 				CDEBUG(D_OTHER, "Re-read last llog buffer for new records, index %u, last %u\n",
 				       index, loghandle->lgh_last_idx);
 				/* save offset inside buffer for the re-read */
-- 
1.8.3.1