On Wed, 29 Nov 2023 at 10:43, Zhao Chen <winters.zc@xxxxxxxxxxxx> wrote:
>
> Some FUSE daemons want to know if the received request is a resend
> request, after writing to the sysfs resend API. The high bit of the fuse
> request id is utilized for indicating this, enabling the receiver to
> perform appropriate handling.
>
> An init flag is added to indicate this feature.
>
> Signed-off-by: Zhao Chen <winters.zc@xxxxxxxxxxxx>
> ---
> fs/fuse/dev.c | 11 +++++++----
> fs/fuse/inode.c | 3 ++-
> include/uapi/linux/fuse.h | 11 +++++++++++
> 3 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index c91cb2bd511b..8a90a41b9a17 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -28,6 +28,7 @@ MODULE_ALIAS("devname:fuse");
> /* Ordinary requests have even IDs, while interrupts IDs are odd */
> #define FUSE_INT_REQ_BIT (1ULL << 0)
> #define FUSE_REQ_ID_STEP (1ULL << 1)
> +#define FUSE_REQ_ID_MASK (~(FUSE_INT_REQ_BIT | FUSE_REQ_ID_RESEND_BIT))
>
> static struct kmem_cache *fuse_req_cachep;
>
> @@ -194,14 +195,14 @@ EXPORT_SYMBOL_GPL(fuse_len_args);
>
> u64 fuse_get_unique(struct fuse_iqueue *fiq)
> {
> - fiq->reqctr += FUSE_REQ_ID_STEP;
> + fiq->reqctr = (fiq->reqctr + FUSE_REQ_ID_STEP) & FUSE_REQ_ID_MASK;
> return fiq->reqctr;
> }
> EXPORT_SYMBOL_GPL(fuse_get_unique);
>
> static unsigned int fuse_req_hash(u64 unique)
> {
> - return hash_long(unique & ~FUSE_INT_REQ_BIT, FUSE_PQ_HASH_BITS);
> + return hash_long(unique & FUSE_REQ_ID_MASK, FUSE_PQ_HASH_BITS);
Possible simplification if FUSE_REQ_ID_RESEND_BIT is not used as a
separate flag, but as a part of the unique request ID. That way
there's no need to mask it out.
> }
>
> /*
> @@ -1813,7 +1814,7 @@ static struct fuse_req *request_find(struct fuse_pqueue *fpq, u64 unique)
> struct fuse_req *req;
>
> list_for_each_entry(req, &fpq->processing[hash], list) {
> - if (req->in.h.unique == unique)
> + if ((req->in.h.unique & FUSE_REQ_ID_MASK) == unique)
Same here.
> return req;
> }
> return NULL;
> @@ -1884,7 +1885,7 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
> spin_lock(&fpq->lock);
> req = NULL;
> if (fpq->connected)
> - req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
> + req = request_find(fpq, oh.unique & FUSE_REQ_ID_MASK);
>
> err = -ENOENT;
> if (!req) {
> @@ -2274,6 +2275,8 @@ void fuse_resend_pqueue(struct fuse_conn *fc)
>
> list_for_each_entry_safe(req, next, &to_queue, list) {
> __set_bit(FR_PENDING, &req->flags);
> + /* mark the request as resend request */
> + req->in.h.unique |= FUSE_REQ_ID_RESEND_BIT;
> }
>
> spin_lock(&fiq->lock);
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 2a6d44f91729..e774865fbfa3 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1330,7 +1330,8 @@ void fuse_send_init(struct fuse_mount *fm)
> FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
> FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |
> FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |
> - FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP;
> + FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP |
> + FUSE_UID_HAS_RESEND_BIT;
> #ifdef CONFIG_FUSE_DAX
> if (fm->fc->dax)
> flags |= FUSE_MAP_ALIGNMENT;
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index e7418d15fe39..ecfb7cbcfe30 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -410,6 +410,8 @@ struct fuse_file_lock {
> * symlink and mknod (single group that matches parent)
> * FUSE_HAS_EXPIRE_ONLY: kernel supports expiry-only entry invalidation
> * FUSE_DIRECT_IO_ALLOW_MMAP: allow shared mmap in FOPEN_DIRECT_IO mode.
> + * FUSE_UID_HAS_RESEND_BIT: use high bit of request ID for indicating resend
> + * requests
> */
> #define FUSE_ASYNC_READ (1 << 0)
> #define FUSE_POSIX_LOCKS (1 << 1)
> @@ -449,6 +451,7 @@ struct fuse_file_lock {
> #define FUSE_CREATE_SUPP_GROUP (1ULL << 34)
> #define FUSE_HAS_EXPIRE_ONLY (1ULL << 35)
> #define FUSE_DIRECT_IO_ALLOW_MMAP (1ULL << 36)
> +#define FUSE_UID_HAS_RESEND_BIT (1ULL << 37)
"FUSE_HAS_RESEND" should be sufficiently descriptive.
>
> /* Obsolete alias for FUSE_DIRECT_IO_ALLOW_MMAP */
> #define FUSE_DIRECT_IO_RELAX FUSE_DIRECT_IO_ALLOW_MMAP
> @@ -960,6 +963,14 @@ struct fuse_fallocate_in {
> uint32_t padding;
> };
>
> +/**
> + * FUSE request unique ID flag
> + *
> + * Indicates whether this is a resend request. The receiver should handle this
> + * request accordingly.
> + */
> +#define FUSE_REQ_ID_RESEND_BIT (1ULL << 63)
How about "FUSE_UNIQUE_RESEND"?
Thanks,
Miklos
