@@ -816,12 +816,13 @@ static int unlock_request(struct fuse_req *req)
return err;
}
-void fuse_copy_init(struct fuse_copy_state *cs, bool write,
- struct iov_iter *iter)
+void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *fc,
+ bool write, struct iov_iter *iter)
{
memset(cs, 0, sizeof(*cs));
cs->write = write;
cs->iter = iter;
+ cs->splice_read_user_pages = fc->splice_read_user_pages;
}
/* Unmap and put previous page of userspace buffer */
@@ -1105,9 +1106,10 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
if (cs->write && cs->pipebufs && page) {
/*
* Can't control lifetime of pipe buffers, so always
- * copy user pages.
+ * copy user pages if server does not support splice
+ * for reading user pages.
*/
- if (cs->req->args->user_pages) {
+ if (cs->req->args->user_pages && !cs->splice_read_user_pages) {
err = fuse_copy_fill(cs);
if (err)
return err;
@@ -1538,7 +1540,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
if (!user_backed_iter(to))
return -EINVAL;
- fuse_copy_init(&cs, true, to);
+ fuse_copy_init(&cs, fud->fc, true, to);
return fuse_dev_do_read(fud, file, &cs, iov_iter_count(to));
}
@@ -1561,7 +1563,7 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
if (!bufs)
return -ENOMEM;
- fuse_copy_init(&cs, true, NULL);
+ fuse_copy_init(&cs, fud->fc, true, NULL);
cs.pipebufs = bufs;
cs.pipe = pipe;
ret = fuse_dev_do_read(fud, in, &cs, len);
@@ -2227,7 +2229,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
if (!user_backed_iter(from))
return -EINVAL;
- fuse_copy_init(&cs, false, from);
+ fuse_copy_init(&cs, fud->fc, false, from);
return fuse_dev_do_write(fud, &cs, iov_iter_count(from));
}
@@ -2301,7 +2303,7 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
}
pipe_unlock(pipe);
- fuse_copy_init(&cs, false, NULL);
+ fuse_copy_init(&cs, fud->fc, false, NULL);
cs.pipebufs = bufs;
cs.nr_segs = nbuf;
cs.pipe = pipe;
@@ -593,7 +593,7 @@ static int fuse_uring_copy_from_ring(struct fuse_ring *ring,
if (err)
return err;
- fuse_copy_init(&cs, false, &iter);
+ fuse_copy_init(&cs, ring->fc, false, &iter);
cs.is_uring = true;
cs.req = req;
@@ -623,7 +623,7 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
return err;
}
- fuse_copy_init(&cs, true, &iter);
+ fuse_copy_init(&cs, ring->fc, true, &iter);
cs.is_uring = true;
cs.req = req;
@@ -32,6 +32,7 @@ struct fuse_copy_state {
bool write:1;
bool move_pages:1;
bool is_uring:1;
+ bool splice_read_user_pages:1;
struct {
unsigned int copied_sz; /* copied size into the user buffer */
} ring;
@@ -51,8 +52,8 @@ struct fuse_req *fuse_request_find(struct fuse_pqueue *fpq, u64 unique);
void fuse_dev_end_requests(struct list_head *head);
-void fuse_copy_init(struct fuse_copy_state *cs, bool write,
- struct iov_iter *iter);
+void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *conn,
+ bool write, struct iov_iter *iter);
int fuse_copy_args(struct fuse_copy_state *cs, unsigned int numargs,
unsigned int argpages, struct fuse_arg *args,
int zeroing);
@@ -898,6 +898,9 @@ struct fuse_conn {
/* Use io_uring for communication */
bool io_uring:1;
+ /* Allow splice for reading user pages */
+ bool splice_read_user_pages:1;
+
/** Maximum stack depth for passthrough backing files */
int max_stack_depth;
@@ -1439,6 +1439,9 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
if (flags & FUSE_REQUEST_TIMEOUT)
timeout = arg->request_timeout;
+
+ if (flags & FUSE_SPLICE_READ_USER_PAGES)
+ fc->splice_read_user_pages = true;
} else {
ra_pages = fc->max_read / PAGE_SIZE;
fc->no_lock = true;
@@ -1489,7 +1492,7 @@ void fuse_send_init(struct fuse_mount *fm)
FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |
FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP |
FUSE_NO_EXPORT_SUPPORT | FUSE_HAS_RESEND | FUSE_ALLOW_IDMAP |
- FUSE_REQUEST_TIMEOUT;
+ FUSE_REQUEST_TIMEOUT | FUSE_SPLICE_READ_USER_PAGES;
#ifdef CONFIG_FUSE_DAX
if (fm->fc->dax)
flags |= FUSE_MAP_ALIGNMENT;
@@ -235,6 +235,9 @@
*
* 7.44
* - add FUSE_NOTIFY_INC_EPOCH
+ *
+ * 7.45
+ * - add FUSE_SPLICE_READ_USER_PAGES
*/
#ifndef _LINUX_FUSE_H
@@ -443,6 +446,10 @@ struct fuse_file_lock {
* FUSE_OVER_IO_URING: Indicate that client supports io-uring
* FUSE_REQUEST_TIMEOUT: kernel supports timing out requests.
* init_out.request_timeout contains the timeout (in secs)
+ * FUSE_SPLICE_READ_USER_PAGES: kernel supports splice on the device for reading
+ * user pages. If the server enables this, then the
+ * server should not access the pipe buffer after
+ * completing the request.
*/
#define FUSE_ASYNC_READ (1 << 0)
#define FUSE_POSIX_LOCKS (1 << 1)
@@ -490,6 +497,7 @@ struct fuse_file_lock {
#define FUSE_ALLOW_IDMAP (1ULL << 40)
#define FUSE_OVER_IO_URING (1ULL << 41)
#define FUSE_REQUEST_TIMEOUT (1ULL << 42)
+#define FUSE_SPLICE_READ_USER_PAGES (1ULL << 43)
/**
* CUSE INIT request/reply flags
For direct io writes, splice is disabled when forwarding pages from the client to the server. This is because the pages in the pipe buffer are user pages, which is controlled by the client. Thus if a server replies to the request and then keeps accessing the pages afterwards, there is the possibility that the client may have modified the contents of the pages in the meantime. More context on this can be found in commit 0c4bcfdecb1a ("fuse: fix pipe buffer lifetime for direct_io"). For servers that do not need to access pages after answering the request, splice gives a non-trivial improvement in performance. Benchmarks show roughly a 40% speedup. Allow servers to enable zero-copy splice for servicing client direct io writes. By enabling this, the server understands that they should not continue accessing the pipe buffer after completing the request or may face incorrect data if they do so. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> --- fs/fuse/dev.c | 18 ++++++++++-------- fs/fuse/dev_uring.c | 4 ++-- fs/fuse/fuse_dev_i.h | 5 +++-- fs/fuse/fuse_i.h | 3 +++ fs/fuse/inode.c | 5 ++++- include/uapi/linux/fuse.h | 8 ++++++++ 6 files changed, 30 insertions(+), 13 deletions(-)