verity_ctr() creates a dedicated dm_io_client (v->io) for every
dm-verity target, but its only caller is verity_recheck(), which reads
a single data block into a page from v->recheck_pool after a hash
mismatch. Because dm_io_client_create() preallocates a mempool of 16
bios and 16 biovec-max (4 KiB) vectors per target, each dm-verity
target permanently pins ~70 KiB of unreclaimable slab that a single-page
read never uses (~2.4 MiB across 35 targets on Android, or ~4.1 MiB
across 59 targets).
Replace dm_io() in verity_recheck() with bdev_rw_virt() and remove
v->io. bdev_rw_virt() puts the bio and single bio_vec on the stack and
waits for completion, while keeping v->recheck_pool per-target.
Fixes: 9177f3c0dea6 ("dm-verity: recheck the hash after a failure")
Link:
https://lore.kernel.org/dm-devel/[email protected]/
Signed-off-by: Chris Wiseman <[email protected]>
---
TEST (ARM64 QEMU, 59 dm-verity targets, sha256, 4K blocks, mem_profiling=1):
/proc/allocinfo growth from 0 to 35 targets (bytes):
BASE PATCHED DELTA
bio.c:biovec_init_pool 4,587,520 2,293,760 -2,293,760
bio.c:bioset_init 1,196,160 1,052,800 -143,360
dm-io.c:dm_io_client_create 107,520 53,760 -53,760
mempool.c:mempool_init_node 36,680 23,240 -13,440
Total (35 targets) 5,927,880 3,423,560 -2,504,320 (-71,552
B/target)
Unreclaimable slab saved by target count:
8 targets: 572,416 B ( 559 KiB)
15 targets: 1,073,280 B (1,048 KiB)
35 targets: 2,504,320 B (2,446 KiB) [SUnreclaim: BASE +8,436 kB vs PATCHED
+5,960 kB]
59 targets: 4,221,568 B (4,123 KiB)
drivers/md/dm-verity-target.c | 24 +++---------------------
drivers/md/dm-verity.h | 2 --
2 files changed, 3 insertions(+), 23 deletions(-)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 6d589867623c..7c240b3a470f 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -379,21 +379,13 @@ static noinline int verity_recheck(struct dm_verity *v,
struct dm_verity_io *io,
struct page *page;
void *buffer;
int r;
- struct dm_io_request io_req;
- struct dm_io_region io_loc;
page = mempool_alloc(&v->recheck_pool, GFP_NOIO);
buffer = page_to_virt(page);
- io_req.bi_opf = REQ_OP_READ;
- io_req.mem.type = DM_IO_KMEM;
- io_req.mem.ptr.addr = buffer;
- io_req.notify.fn = NULL;
- io_req.client = v->io;
- io_loc.bdev = v->data_dev->bdev;
- io_loc.sector = cur_block << (v->data_dev_block_bits - SECTOR_SHIFT);
- io_loc.count = 1 << (v->data_dev_block_bits - SECTOR_SHIFT);
- r = dm_io(&io_req, 1, &io_loc, NULL, NULL, IOPRIO_DEFAULT);
+ r = bdev_rw_virt(v->data_dev->bdev,
+ cur_block << (v->data_dev_block_bits - SECTOR_SHIFT),
+ buffer, 1 << v->data_dev_block_bits, REQ_OP_READ);
if (unlikely(r))
goto free_ret;
@@ -1058,8 +1050,6 @@ static void verity_dtr(struct dm_target *ti)
destroy_workqueue(v->verify_wq);
mempool_exit(&v->recheck_pool);
- if (v->io)
- dm_io_client_destroy(v->io);
if (v->bufio)
dm_bufio_client_destroy(v->bufio);
@@ -1604,14 +1594,6 @@ static int verity_ctr(struct dm_target *ti, unsigned int
argc, char **argv)
goto bad;
}
- v->io = dm_io_client_create();
- if (IS_ERR(v->io)) {
- r = PTR_ERR(v->io);
- v->io = NULL;
- ti->error = "Cannot allocate dm io";
- goto bad;
- }
-
v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
dm_bufio_alloc_callback, NULL,
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index e104a651c657..0c42ac99e631 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -11,7 +11,6 @@
#ifndef DM_VERITY_H
#define DM_VERITY_H
-#include <linux/dm-io.h>
#include <linux/dm-bufio.h>
#include <linux/device-mapper.h>
#include <linux/interrupt.h>
@@ -80,7 +79,6 @@ struct dm_verity {
char *signature_key_desc; /* signature keyring reference */
- struct dm_io_client *io;
mempool_t recheck_pool;
};
--
2.56.0
