2024-01-04 01:57:23

by Hou Tao

Subject: [PATCH] virtiofs: use GFP_NOFS when enqueuing request through kworker

From: Hou Tao <[email protected]>

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 both the sg array and the bounce buffer may be
greater than PAGE_SIZE, use GFP_NOFS instead of GFP_ATOMIC to lower the
possibility of memory allocation failure.

Signed-off-by: Hou Tao <[email protected]>
---
fs/fuse/virtio_fs.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 3aac31d45198..ec4d0d81a5e2 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -87,7 +87,8 @@ 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,
+ bool in_atomic);

static const struct constant_table dax_param_enums[] = {
{"always", FUSE_DAX_ALWAYS },
@@ -383,7 +384,7 @@ 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);
+ ret = virtio_fs_enqueue_req(fsvq, req, true, false);
if (ret < 0) {
if (ret == -ENOMEM || ret == -ENOSPC) {
spin_lock(&fsvq->lock);
@@ -488,7 +489,7 @@ 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;
@@ -502,7 +503,7 @@ 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;

@@ -1119,7 +1120,8 @@ 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,
+ bool in_atomic)
{
/* requests need at least 4 elements */
struct scatterlist *stack_sgs[6];
@@ -1128,6 +1130,7 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
struct scatterlist *sg = stack_sg;
struct virtqueue *vq;
struct fuse_args *args = req->args;
+ gfp_t gfp = in_atomic ? GFP_ATOMIC : GFP_NOFS;
unsigned int argbuf_used = 0;
unsigned int out_sgs = 0;
unsigned int in_sgs = 0;
@@ -1140,8 +1143,8 @@ 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;
@@ -1149,7 +1152,7 @@ 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;

@@ -1245,7 +1248,7 @@ __releases(fiq->lock)
fuse_len_args(req->args->out_numargs, req->args->out_args));

fsvq = &fs->vqs[queue_id];
- ret = virtio_fs_enqueue_req(fsvq, req, false);
+ ret = virtio_fs_enqueue_req(fsvq, req, false, true);
if (ret < 0) {
if (ret == -ENOMEM || ret == -ENOSPC) {
/*
--
2.29.2

2024-01-04 02:56:03

by Matthew Wilcox

Subject: Re: [PATCH] virtiofs: use GFP_NOFS when enqueuing request through kworker

On Thu, Jan 04, 2024 at 09:58:05AM +0800, Hou Tao wrote:
> 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,
> + bool in_atomic);

Better to pass the gfp_t directly instead of a bool.