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mm: zswap: move allocations during CPU init outside the lock

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In zswap_cpu_comp_prepare(), allocations are made and assigned to various
members of acomp_ctx under acomp_ctx->mutex.  However, allocations may
recurse into zswap through reclaim, trying to acquire the same mutex and
deadlocking.

Move the allocations before the mutex critical section.  Only the
initialization of acomp_ctx needs to be done with the mutex held.

Link: https://lkml.kernel.org/r/20250113214458.2123410-1-yosryahmed@google.com
Fixes: 12dcb0ef54 ("mm: zswap: properly synchronize freeing resources during CPU hotunplug")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yosry Ahmed 2025-01-13 21:44:58 +00:00 committed by Andrew Morton
parent f1897f2f08
commit 779b9955f6
1 changed files with 24 additions and 18 deletions
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42
mm/zswap.c
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@ -820,15 +820,15 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
{
struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
struct crypto_acomp *acomp;
struct acomp_req *req;
struct crypto_acomp *acomp = NULL;
struct acomp_req *req = NULL;
u8 *buffer = NULL;
int ret;
mutex_lock(&acomp_ctx->mutex);
acomp_ctx->buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
if (!acomp_ctx->buffer) {
buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
if (!buffer) {
ret = -ENOMEM;
goto buffer_fail;
goto fail;
}
acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
@ -836,21 +836,25 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
pr_err("could not alloc crypto acomp %s : %ld\n",
pool->tfm_name, PTR_ERR(acomp));
ret = PTR_ERR(acomp);
goto acomp_fail;
goto fail;
}
acomp_ctx->acomp = acomp;
acomp_ctx->is_sleepable = acomp_is_async(acomp);
req = acomp_request_alloc(acomp_ctx->acomp);
req = acomp_request_alloc(acomp);
if (!req) {
pr_err("could not alloc crypto acomp_request %s\n",
pool->tfm_name);
ret = -ENOMEM;
goto req_fail;
goto fail;
}
acomp_ctx->req = req;
/*
* Only hold the mutex after completing allocations, otherwise we may
* recurse into zswap through reclaim and attempt to hold the mutex
* again resulting in a deadlock.
*/
mutex_lock(&acomp_ctx->mutex);
crypto_init_wait(&acomp_ctx->wait);
/*
* if the backend of acomp is async zip, crypto_req_done() will wakeup
* crypto_wait_req(); if the backend of acomp is scomp, the callback
@ -859,15 +863,17 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
crypto_req_done, &acomp_ctx->wait);
acomp_ctx->buffer = buffer;
acomp_ctx->acomp = acomp;
acomp_ctx->is_sleepable = acomp_is_async(acomp);
acomp_ctx->req = req;
mutex_unlock(&acomp_ctx->mutex);
return 0;
req_fail:
crypto_free_acomp(acomp_ctx->acomp);
acomp_fail:
kfree(acomp_ctx->buffer);
buffer_fail:
mutex_unlock(&acomp_ctx->mutex);
fail:
if (acomp)
crypto_free_acomp(acomp);
kfree(buffer);
return ret;
}