* [dm-devel] [PATCH] dm-integrity: don't write metadata if we overwrite it with the same content
@ 2021-04-27 15:57 Mikulas Patocka
0 siblings, 0 replies; only message in thread
From: Mikulas Patocka @ 2021-04-27 15:57 UTC (permalink / raw)
To: Mike Snitzer, Milan Broz; +Cc: dm-devel, Melvin Vermeeren
If we discard already discarded blocks, we do not need to write discard
filler to the metadata, because it is already there.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Index: linux-2.6/drivers/md/dm-integrity.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-integrity.c
+++ linux-2.6/drivers/md/dm-integrity.c
@@ -1429,8 +1429,10 @@ static int dm_integrity_rw_tag(struct dm
if (op == TAG_READ) {
memcpy(tag, dp, to_copy);
} else if (op == TAG_WRITE) {
- memcpy(dp, tag, to_copy);
- dm_bufio_mark_partial_buffer_dirty(b, *metadata_offset, *metadata_offset + to_copy);
+ if (memcmp(dp, tag, to_copy)) {
+ memcpy(dp, tag, to_copy);
+ dm_bufio_mark_partial_buffer_dirty(b, *metadata_offset, *metadata_offset + to_copy);
+ }
} else {
/* e.g.: op == TAG_CMP */
--
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