[PATCH v4 2/2] virtiofs: use GFP_NOFS when enqueuing request through kworker
From: Hou Tao <hidden>
Date: 2024-08-31 09:37:56
Also in:
linux-fsdevel, lkml
Subsystem:
filesystems (vfs and infrastructure), fuse filesystem [core], the rest, virtio file system · Maintainers:
Alexander Viro, Christian Brauner, Miklos Szeredi, Linus Torvalds, German Maglione, Vivek Goyal, Stefan Hajnoczi
From: Hou Tao <redacted>
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 <redacted>
---
fs/fuse/virtio_fs.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 43d66ab5e891..9bc48b3ca384 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c@@ -95,7 +95,8 @@ 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 },
@@ -439,6 +440,8 @@ 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);
@@ -449,7 +452,9 @@ 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);
@@ -550,7 +555,7 @@ 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;
@@ -564,7 +569,7 @@ 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;
@@ -1239,7 +1244,8 @@ 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];
@@ -1260,8 +1266,8 @@ 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;
@@ -1269,7 +1275,7 @@ 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;
@@ -1367,7 +1373,7 @@ __releases(fiq->lock) 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) { /*
--
2.29.2