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| author | Connor Kuehl <ckuehl@redhat.com> | 2021-03-18 08:52:22 -0500 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2021-04-14 10:40:57 +0200 |
| commit | a7f0d7aab0b4f3f0780b1f77356e2fe7202ac0cb (patch) | |
| tree | aeaccd4413406edb9128aa1f9794d7337c7e66c9 /fs/fuse/inode.c | |
| parent | c79c5e0178922a9e092ec8fed026750f39dcaef4 (diff) | |
| download | linux-a7f0d7aab0b4f3f0780b1f77356e2fe7202ac0cb.tar.bz2 | |
virtiofs: split requests that exceed virtqueue size
If an incoming FUSE request can't fit on the virtqueue, the request is
placed onto a workqueue so a worker can try to resubmit it later where
there will (hopefully) be space for it next time.
This is fine for requests that aren't larger than a virtqueue's maximum
capacity. However, if a request's size exceeds the maximum capacity of the
virtqueue (even if the virtqueue is empty), it will be doomed to a life of
being placed on the workqueue, removed, discovered it won't fit, and placed
on the workqueue yet again.
Furthermore, from section 2.6.5.3.1 (Driver Requirements: Indirect
Descriptors) of the virtio spec:
"A driver MUST NOT create a descriptor chain longer than the Queue
Size of the device."
To fix this, limit the number of pages FUSE will use for an overall
request. This way, each request can realistically fit on the virtqueue
when it is decomposed into a scattergather list and avoid violating section
2.6.5.3.1 of the virtio spec.
Signed-off-by: Connor Kuehl <ckuehl@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/fuse/inode.c')
| -rw-r--r-- | fs/fuse/inode.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 06a68cfa76d8..2f3161bb4b1c 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -712,6 +712,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm, fc->pid_ns = get_pid_ns(task_active_pid_ns(current)); fc->user_ns = get_user_ns(user_ns); fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ; + fc->max_pages_limit = FUSE_MAX_MAX_PAGES; INIT_LIST_HEAD(&fc->mounts); list_add(&fm->fc_entry, &fc->mounts); @@ -1040,7 +1041,7 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, fc->abort_err = 1; if (arg->flags & FUSE_MAX_PAGES) { fc->max_pages = - min_t(unsigned int, FUSE_MAX_MAX_PAGES, + min_t(unsigned int, fc->max_pages_limit, max_t(unsigned int, arg->max_pages, 1)); } if (IS_ENABLED(CONFIG_FUSE_DAX) && |