From: "xianrong.zhou" xianrong.zhou@transsion.com
mainline inclusion from mainline-5.6-rc1 commit 0a531c5a39a71279e0a98097562bf14b5a43529e category: bugfix bugzilla: 29444 CVE: NA ---------------------------
Try to skip prefetching hash blocks that won't be needed due to the "check_at_most_once" option being enabled and the corresponding data blocks already having been verified.
Since prefetching operates on a range of data blocks, do this by just trimming the two ends of the range. This doesn't skip every unneeded hash block, since data blocks in the middle of the range could also be unneeded, and hash blocks are still prefetched in large clusters as controlled by dm_verity_prefetch_cluster. But it can still help a lot.
In a test on Android Q launching 91 apps every 15s repeated 21 times, prefetching was only done for 447177/4776629 = 9.36% of data blocks.
Tested-by: ruxian.feng ruxian.feng@transsion.com Co-developed-by: yuanjiong.gao yuanjiong.gao@transsion.com Signed-off-by: yuanjiong.gao yuanjiong.gao@transsion.com Signed-off-by: xianrong.zhou xianrong.zhou@transsion.com [EB: simplified the 'while' loops and improved the commit message] Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Sun Ke sunke32@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/md/dm-verity-target.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index e3599b4..50ab1af 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -611,8 +611,22 @@ static void verity_prefetch_io(struct work_struct *work)
static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io) { + sector_t block = io->block; + unsigned int n_blocks = io->n_blocks; struct dm_verity_prefetch_work *pw;
+ if (v->validated_blocks) { + while (n_blocks && test_bit(block, v->validated_blocks)) { + block++; + n_blocks--; + } + while (n_blocks && test_bit(block + n_blocks - 1, + v->validated_blocks)) + n_blocks--; + if (!n_blocks) + return; + } + pw = kmalloc(sizeof(struct dm_verity_prefetch_work), GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
@@ -621,8 +635,8 @@ static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
INIT_WORK(&pw->work, verity_prefetch_io); pw->v = v; - pw->block = io->block; - pw->n_blocks = io->n_blocks; + pw->block = block; + pw->n_blocks = n_blocks; queue_work(v->verify_wq, &pw->work); }