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Subject[PATCH v2] async_pq: Remove VLA usage
Date
In the quest to remove VLAs from the kernel[1], this moves the
allocation of coefs and blocks from the stack to being kmalloc()ed.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Kyle Spiers <ksspiers@google.com>
---
Forgot to add slab.h
---
crypto/async_tx/async_pq.c | 18 ++++++++++++++----
crypto/async_tx/raid6test.c | 9 ++++++++-
2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
index 56bd612927ab..af1912313a23 100644
--- a/crypto/async_tx/async_pq.c
+++ b/crypto/async_tx/async_pq.c
@@ -194,9 +194,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
(src_cnt <= dma_maxpq(device, 0) ||
dma_maxpq(device, DMA_PREP_CONTINUE) > 0) &&
is_dma_pq_aligned(device, offset, 0, len)) {
- struct dma_async_tx_descriptor *tx;
+ struct dma_async_tx_descriptor *tx = NULL;
enum dma_ctrl_flags dma_flags = 0;
- unsigned char coefs[src_cnt];
+ unsigned char *coefs;
int i, j;

/* run the p+q asynchronously */
@@ -207,6 +207,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
* sources and update the coefficients accordingly
*/
unmap->len = len;
+ coefs = kmalloc_array(src_cnt, sizeof(*coefs), GFP_KERNEL);
+ if (!coefs)
+ goto out;
for (i = 0, j = 0; i < src_cnt; i++) {
if (blocks[i] == NULL)
continue;
@@ -240,7 +243,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
}

tx = do_async_gen_syndrome(chan, coefs, j, unmap, dma_flags, submit);
+out:
dmaengine_unmap_put(unmap);
+ kfree(coefs);
return tx;
}

@@ -298,8 +303,8 @@ async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
{
struct dma_chan *chan = pq_val_chan(submit, blocks, disks, len);
struct dma_device *device = chan ? chan->device : NULL;
- struct dma_async_tx_descriptor *tx;
- unsigned char coefs[disks-2];
+ struct dma_async_tx_descriptor *tx = NULL;
+ unsigned char *coefs = NULL;
enum dma_ctrl_flags dma_flags = submit->cb_fn ? DMA_PREP_INTERRUPT : 0;
struct dmaengine_unmap_data *unmap = NULL;

@@ -318,6 +323,9 @@ async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
__func__, disks, len);

unmap->len = len;
+ coefs = kmalloc_array(disks - 2, sizeof(*coefs), GFP_KERNEL);
+ if (!coefs)
+ goto out;
for (i = 0; i < disks-2; i++)
if (likely(blocks[i])) {
unmap->addr[j] = dma_map_page(dev, blocks[i],
@@ -423,6 +431,8 @@ async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
async_tx_sync_epilog(submit);
tx = NULL;
}
+out:
+ kfree(coefs);
dmaengine_unmap_put(unmap);

return tx;
diff --git a/crypto/async_tx/raid6test.c b/crypto/async_tx/raid6test.c
index dad95f45b88f..4237a5ae8f42 100644
--- a/crypto/async_tx/raid6test.c
+++ b/crypto/async_tx/raid6test.c
@@ -24,6 +24,7 @@
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/module.h>
+#include <linux/slab.h>

#undef pr
#define pr(fmt, args...) pr_info("raid6test: " fmt, ##args)
@@ -81,11 +82,16 @@ static void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, stru
init_async_submit(&submit, 0, NULL, NULL, NULL, addr_conv);
tx = async_gen_syndrome(ptrs, 0, disks, bytes, &submit);
} else {
- struct page *blocks[disks];
+ struct page **blocks;
struct page *dest;
int count = 0;
int i;

+ blocks = kmalloc_array(disks, sizeof(*blocks),
+ GFP_KERNEL);
+ if (!blocks)
+ return;
+
/* data+Q failure. Reconstruct data from P,
* then rebuild syndrome
*/
@@ -101,6 +107,7 @@ static void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, stru

init_async_submit(&submit, 0, tx, NULL, NULL, addr_conv);
tx = async_gen_syndrome(ptrs, 0, disks, bytes, &submit);
+ kfree(blocks);
}
} else {
if (failb == disks-2) {
--
2.17.0.441.gb46fe60e1d-goog
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