Patch "dm integrity: fix inefficient allocation of journal space" has been added to the 4.12-stable tree

Patch "dm integrity: fix inefficient allocation of journal space" has been added to the 4.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    dm integrity: fix inefficient allocation of journal space

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-integrity-fix-inefficient-allocation-of-journal-space.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9dd59727dbc21d33a9add4c5b308a5775cd5a6ef Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 19 Jul 2017 11:23:40 -0400
Subject: dm integrity: fix inefficient allocation of journal space

From: Mikulas Patocka <mpatocka@redhat.com>

commit 9dd59727dbc21d33a9add4c5b308a5775cd5a6ef upstream.

When using a block size greater than 512 bytes, the dm-integrity target
allocates journal space inefficiently.  It allocates one journal entry
for each 512-byte chunk of data, fills an entry for each block of data
and leaves the remaining entries unused.

This issue doesn't cause data corruption, but all the unused journal
entries degrade performance severely.

For example, with 4k blocks and an 8k bio, it would allocate 16 journal
entries but only use 2 entries.  The remaining 14 entries were left
unused.

Fix this by adding the missing 'log2_sectors_per_block' shifts that are
required to have each journal entry map to a full block.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 7eada909bfd7 ("dm: add integrity target")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-integrity.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -1587,16 +1587,18 @@ retry:
 	if (likely(ic->mode == 'J')) {
 		if (dio->write) {
 			unsigned next_entry, i, pos;
-			unsigned ws, we;
+			unsigned ws, we, range_sectors;
 
-			dio->range.n_sectors = min(dio->range.n_sectors, ic->free_sectors);
+			dio->range.n_sectors = min(dio->range.n_sectors,
+						   ic->free_sectors << ic->sb->log2_sectors_per_block);
 			if (unlikely(!dio->range.n_sectors))
 				goto sleep;
-			ic->free_sectors -= dio->range.n_sectors;
+			range_sectors = dio->range.n_sectors >> ic->sb->log2_sectors_per_block;
+			ic->free_sectors -= range_sectors;
 			journal_section = ic->free_section;
 			journal_entry = ic->free_section_entry;
 
-			next_entry = ic->free_section_entry + dio->range.n_sectors;
+			next_entry = ic->free_section_entry + range_sectors;
 			ic->free_section_entry = next_entry % ic->journal_section_entries;
 			ic->free_section += next_entry / ic->journal_section_entries;
 			ic->n_uncommitted_sections += next_entry / ic->journal_section_entries;


Patches currently in stable-queue which might be from mpatocka@redhat.com are

queue-4.12/dm-integrity-fix-inefficient-allocation-of-journal-space.patch
queue-4.12/dm-integrity-test-for-corrupted-disk-format-during-table-load.patch