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virtiofs: use GFP_NOFS when enqueuing request through kworker

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When invoking virtio_fs_enqueue_req() through kworker, both the
allocation of the sg array and the bounce buffer still use GFP_ATOMIC.
Considering the size of the sg array may be greater than PAGE_SIZE, use
GFP_NOFS instead of GFP_ATOMIC to lower the possibility of memory
allocation failure and to avoid unnecessarily depleting the atomic
reserves. GFP_NOFS is not passed to virtio_fs_enqueue_req() directly,
GFP_KERNEL and memalloc_nofs_{save|restore} helpers are used instead.

It may seem OK to pass GFP_NOFS to virtio_fs_enqueue_req() as well when
queuing the request for the first time, but this is not the case. The
reason is that fuse_request_queue_background() may call
->queue_request_and_unlock() while holding fc->bg_lock, which is a
spin-lock. Therefore, still use GFP_ATOMIC for it.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Hou Tao 2024-08-31 17:37:50 +08:00 committed by Miklos Szeredi
parent 41748675c0
commit 86b74eb5a1
1 changed files with 15 additions and 9 deletions
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24
fs/fuse/virtio_fs.c
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@ -97,7 +97,8 @@ struct virtio_fs_req_work {
};
static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
struct fuse_req *req, bool in_flight);
struct fuse_req *req, bool in_flight,
gfp_t gfp);
static const struct constant_table dax_param_enums[] = {
{"always", FUSE_DAX_ALWAYS },
@ -575,6 +576,8 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work)
/* Dispatch pending requests */
while (1) {
unsigned int flags;
spin_lock(&fsvq->lock);
req = list_first_entry_or_null(&fsvq->queued_reqs,
struct fuse_req, list);
@ -585,7 +588,9 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work)
list_del_init(&req->list);
spin_unlock(&fsvq->lock);
ret = virtio_fs_enqueue_req(fsvq, req, true);
flags = memalloc_nofs_save();
ret = virtio_fs_enqueue_req(fsvq, req, true, GFP_KERNEL);
memalloc_nofs_restore(flags);
if (ret < 0) {
if (ret == -ENOSPC) {
spin_lock(&fsvq->lock);
@ -686,7 +691,7 @@ static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
}
/* Allocate and copy args into req->argbuf */
static int copy_args_to_argbuf(struct fuse_req *req)
static int copy_args_to_argbuf(struct fuse_req *req, gfp_t gfp)
{
struct fuse_args *args = req->args;
unsigned int offset = 0;
@ -700,7 +705,7 @@ static int copy_args_to_argbuf(struct fuse_req *req)
len = fuse_len_args(num_in, (struct fuse_arg *) args->in_args) +
fuse_len_args(num_out, args->out_args);
req->argbuf = kmalloc(len, GFP_ATOMIC);
req->argbuf = kmalloc(len, gfp);
if (!req->argbuf)
return -ENOMEM;
@ -1366,7 +1371,8 @@ static unsigned int sg_init_fuse_args(struct scatterlist *sg,
/* Add a request to a virtqueue and kick the device */
static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
struct fuse_req *req, bool in_flight)
struct fuse_req *req, bool in_flight,
gfp_t gfp)
{
/* requests need at least 4 elements */
struct scatterlist *stack_sgs[6];
@ -1387,8 +1393,8 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
/* Does the sglist fit on the stack? */
total_sgs = sg_count_fuse_req(req);
if (total_sgs > ARRAY_SIZE(stack_sgs)) {
sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), GFP_ATOMIC);
sg = kmalloc_array(total_sgs, sizeof(sg[0]), GFP_ATOMIC);
sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), gfp);
sg = kmalloc_array(total_sgs, sizeof(sg[0]), gfp);
if (!sgs || !sg) {
ret = -ENOMEM;
goto out;
@ -1396,7 +1402,7 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
}
/* Use a bounce buffer since stack args cannot be mapped */
ret = copy_args_to_argbuf(req);
ret = copy_args_to_argbuf(req, gfp);
if (ret < 0)
goto out;
@ -1490,7 +1496,7 @@ static void virtio_fs_send_req(struct fuse_iqueue *fiq, struct fuse_req *req)
queue_id);
fsvq = &fs->vqs[queue_id];
ret = virtio_fs_enqueue_req(fsvq, req, false);
ret = virtio_fs_enqueue_req(fsvq, req, false, GFP_ATOMIC);
if (ret < 0) {
if (ret == -ENOSPC) {
/*