On 10/22/25 13:58, Vasileios Almpanis wrote:
When handling multiple concurrent dm-ploop requests, large bio_vec arrays
can be allocated during request processing. These allocations are currently
done with kmalloc_array(GFP_ATOMIC), which can fail under memory pressure
for higher orders (order >= 6, ~256KB). Such failures result in partial or
corrupted I/O, leading to EXT4 directory checksum errors and read-only
remounts under heavy parallel workloads.
This patch adds a fallback mechanism to use kvmalloc_array for
large or failed allocations. If the estimated allocation order is >= 6, or
if the kmalloc_array allocation fails. This avoids high-order GFP_ATOMIC
allocations from interrupt context and ensures more reliable memory allocation
behavior.
https://virtuozzo.atlassian.net/browse/VSTOR-109595
Signed-off-by: Vasileios Almpanis <[email protected]>
Feature: dm-ploop: ploop target driver
---
drivers/md/dm-ploop-map.c | 46 ++++++++++++++++++++++++++++++---------
drivers/md/dm-ploop.h | 1 +
2 files changed, 37 insertions(+), 10 deletions(-)
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 3fb841f8bcea..899b9bf088b3 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -16,6 +16,7 @@
#include <linux/error-injection.h>
#include <linux/uio.h>
#include <linux/blk-mq.h>
+#include <linux/mm.h>
#include <uapi/linux/falloc.h>
#include "dm-ploop.h"
#include "dm-rq.h"
@@ -89,6 +90,7 @@ void ploop_init_pio(struct ploop *ploop, unsigned int bi_op,
struct pio *pio)
pio->ref_index = PLOOP_REF_INDEX_INVALID;
pio->queue_list_id = PLOOP_LIST_DEFERRED;
pio->bi_status = BLK_STS_OK;
+ pio->use_kvmalloc = false;
atomic_set(&pio->remaining, 1);
pio->piwb = NULL;
INIT_LIST_HEAD(&pio->list);
@@ -193,8 +195,12 @@ static void ploop_prq_endio(struct pio *pio, void *prq_ptr,
struct ploop_rq *prq = prq_ptr;
struct request *rq = prq->rq;
- if (prq->bvec)
- kfree(prq->bvec);
+ if (prq->bvec) {
+ if (pio->use_kvmalloc)
+ kvfree(prq->bvec);
+ else
+ kfree(prq->bvec);
+ }
This does not make any sense. Just kvfree. This will do the trick.
Please check :-)
In that case boolean will not be needed too.
if (prq->css)
css_put(prq->css);
/*
@@ -1963,26 +1969,40 @@ void ploop_index_wb_submit(struct ploop *ploop, struct
ploop_index_wb *piwb)
ploop_runners_add_work(ploop, pio);
}
-static struct bio_vec *ploop_create_bvec_from_rq(struct request *rq)
+static struct bio_vec *ploop_create_bvec_from_rq(struct request *rq, bool
use_kvmalloc)
pass GFP_MASK from upper level, that would be simplear.
{
struct bio_vec bv, *bvec, *tmp;
struct req_iterator rq_iter;
unsigned int nr_bvec = 0;
+ unsigned int order = 0;
rq_for_each_bvec(bv, rq, rq_iter)
nr_bvec++;
- bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
- GFP_ATOMIC);
- if (!bvec)
- goto out;
+ if (use_kvmalloc) {
+ bvec = kvmalloc_array(nr_bvec, sizeof(struct bio_vec),
+ GFP_NOIO);
+ if (!bvec)
+ return ERR_PTR(-ENOMEM);
+ } else {
+ order = get_order(nr_bvec * sizeof(struct bio_vec));
+ /*
+ * order 6 is 262144 bytes. Lets defer such big
+ * allocations to workqueue.
+ */
+ if (order >= 6)
+ return ERR_PTR(-EAGAIN);
+ bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
+ GFP_ATOMIC | __GFP_NOWARN);
+ if (!bvec)
+ return ERR_PTR(-EAGAIN);
+ }
tmp = bvec;
rq_for_each_bvec(bv, rq, rq_iter) {
*tmp = bv;
tmp++;
}
-out:
return bvec;
}
ALLOW_ERROR_INJECTION(ploop_create_bvec_from_rq, NULL);
@@ -2003,9 +2023,15 @@ static void ploop_prepare_one_embedded_pio(struct ploop
*ploop,
* Transform a set of bvec arrays related to bios
* into a single bvec array (which we can iterate).
*/
- bvec = ploop_create_bvec_from_rq(rq);
- if (!bvec)
+ bvec = ploop_create_bvec_from_rq(rq, pio->use_kvmalloc);
+ if (IS_ERR(bvec)) {
+ if (PTR_ERR(bvec) == -EAGAIN) {
+ pio->use_kvmalloc = true;
+ llist_add((struct llist_node *)(&pio->list),
&ploop->pios[PLOOP_LIST_PREPARE]);
+ return;
+ }
goto err_nomem;
+ }
prq->bvec = bvec;
skip_bvec:
pio->bi_iter.bi_size = blk_rq_bytes(rq);
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index fc12efeb0cd9..53e8d12064bd 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -316,6 +316,7 @@ struct pio {
unsigned int ref_index:2;
u8 queue_list_id; /* id in ploop->pios */
+ bool use_kvmalloc;
struct ploop_index_wb *piwb;
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