From: Amir Goldstein <amir73il@gmail.com> mainline inclusion from mainline-v6.9-rc1 commit 7dc4e97a4f9a55bae6ed6ab3f96c92921259d59f category: feature bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBHLU4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- FUSE_PASSTHROUGH capability to passthrough FUSE operations to backing files will be made available with kernel config CONFIG_FUSE_PASSTHROUGH. When requesting FUSE_PASSTHROUGH, userspace needs to specify the max_stack_depth that is allowed for FUSE on top of backing files. Introduce the flag FOPEN_PASSTHROUGH and backing_id to fuse_open_out argument that can be used when replying to OPEN request, to setup passthrough of io operations on the fuse inode to a backing file. Introduce a refcounted fuse_backing object that will be used to associate an open backing file with a fuse inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Conflicts: fs/fuse/fuse_i.h Signed-off-by: Yifan Qiao <qiaoyifan4@huawei.com> --- fs/fuse/fuse_i.h | 42 +++++++++++++++++++++++++++++++++++++++ include/uapi/linux/fuse.h | 14 ++++++++++--- fs/fuse/inode.c | 26 ++++++++++++++++++++++++ fs/fuse/passthrough.c | 30 ++++++++++++++++++++++++++++ fs/fuse/Kconfig | 11 ++++++++++ fs/fuse/Makefile | 1 + 6 files changed, 121 insertions(+), 3 deletions(-) create mode 100644 fs/fuse/passthrough.c diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 5cd7bd9b9c29..350eb5ed5578 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -77,6 +77,15 @@ struct fuse_submount_lookup { struct fuse_forget_link *forget; }; +/** Container for data related to mapping to backing file */ +struct fuse_backing { + struct file *file; + + /** refcount */ + refcount_t count; + struct rcu_head rcu; +}; + /** FUSE inode */ struct fuse_inode { /** Inode data */ @@ -180,6 +189,10 @@ struct fuse_inode { #endif /** Submount specific lookup tracking */ struct fuse_submount_lookup *submount_lookup; +#ifdef CONFIG_FUSE_PASSTHROUGH + /** Reference to backing file in passthrough mode */ + struct fuse_backing *fb; +#endif KABI_RESERVE(1) }; @@ -840,6 +853,12 @@ struct fuse_conn { /* Use pages instead of pointer for kernel I/O */ unsigned int use_pages_for_kvec_io:1; + /** Passthrough support for read/write IO */ + unsigned int passthrough:1; + + /** Maximum stack depth for passthrough backing files */ + int max_stack_depth; + /** The number of requests waiting for completion */ atomic_t num_waiting; @@ -1384,4 +1403,27 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid, void fuse_file_release(struct inode *inode, struct fuse_file *ff, unsigned int open_flags, fl_owner_t id, bool isdir); +/* passthrough.c */ +static inline struct fuse_backing *fuse_inode_backing(struct fuse_inode *fi) +{ +#ifdef CONFIG_FUSE_PASSTHROUGH + return READ_ONCE(fi->fb); +#else + return NULL; +#endif +} + +static inline struct fuse_backing *fuse_inode_backing_set(struct fuse_inode *fi, + struct fuse_backing *fb) +{ +#ifdef CONFIG_FUSE_PASSTHROUGH + return xchg(&fi->fb, fb); +#else + return NULL; +#endif +} + +struct fuse_backing *fuse_backing_get(struct fuse_backing *fb); +void fuse_backing_put(struct fuse_backing *fb); + #endif /* _FS_FUSE_I_H */ diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index e7418d15fe39..7bb6219cfda0 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -211,6 +211,10 @@ * 7.39 * - add FUSE_DIRECT_IO_ALLOW_MMAP * - add FUSE_STATX and related structures + * + * 7.40 + * - add max_stack_depth to fuse_init_out, add FUSE_PASSTHROUGH init flag + * - add backing_id to fuse_open_out, add FOPEN_PASSTHROUGH open flag */ #ifndef _LINUX_FUSE_H @@ -246,7 +250,7 @@ #define FUSE_KERNEL_VERSION 7 /** Minor version number of this interface */ -#define FUSE_KERNEL_MINOR_VERSION 39 +#define FUSE_KERNEL_MINOR_VERSION 40 /** The node ID of the root inode */ #define FUSE_ROOT_ID 1 @@ -353,6 +357,7 @@ struct fuse_file_lock { * FOPEN_STREAM: the file is stream-like (no file position at all) * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE) * FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode + * FOPEN_PASSTHROUGH: passthrough read/write io for this open file */ #define FOPEN_DIRECT_IO (1 << 0) #define FOPEN_KEEP_CACHE (1 << 1) @@ -361,6 +366,7 @@ struct fuse_file_lock { #define FOPEN_STREAM (1 << 4) #define FOPEN_NOFLUSH (1 << 5) #define FOPEN_PARALLEL_DIRECT_WRITES (1 << 6) +#define FOPEN_PASSTHROUGH (1 << 7) /** * INIT request/reply flags @@ -449,6 +455,7 @@ 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_PASSTHROUGH (1ULL << 37) /* Obsolete alias for FUSE_DIRECT_IO_ALLOW_MMAP */ #define FUSE_DIRECT_IO_RELAX FUSE_DIRECT_IO_ALLOW_MMAP @@ -761,7 +768,7 @@ struct fuse_create_in { struct fuse_open_out { uint64_t fh; uint32_t open_flags; - uint32_t padding; + int32_t backing_id; }; struct fuse_release_in { @@ -877,7 +884,8 @@ struct fuse_init_out { uint16_t max_pages; uint16_t map_alignment; uint32_t flags2; - uint32_t unused[7]; + uint32_t max_stack_depth; + uint32_t unused[6]; }; #define CUSE_INIT_INFO_MAX 4096 diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 735abf426a06..89e77b136879 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -111,6 +111,9 @@ static struct inode *fuse_alloc_inode(struct super_block *sb) if (IS_ENABLED(CONFIG_FUSE_DAX) && !fuse_dax_inode_alloc(sb, fi)) goto out_free_forget; + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + fuse_inode_backing_set(fi, NULL); + return &fi->inode; out_free_forget: @@ -129,6 +132,9 @@ static void fuse_free_inode(struct inode *inode) #ifdef CONFIG_FUSE_DAX kfree(fi->dax); #endif + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + fuse_backing_put(fuse_inode_backing(fi)); + kmem_cache_free(fuse_inode_cachep, fi); } @@ -1312,6 +1318,24 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, fc->create_supp_group = 1; if (flags & FUSE_DIRECT_IO_ALLOW_MMAP) fc->direct_io_allow_mmap = 1; + /* + * max_stack_depth is the max stack depth of FUSE fs, + * so it has to be at least 1 to support passthrough + * to backing files. + * + * with max_stack_depth > 1, the backing files can be + * on a stacked fs (e.g. overlayfs) themselves and with + * max_stack_depth == 1, FUSE fs can be stacked as the + * underlying fs of a stacked fs (e.g. overlayfs). + */ + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH) && + (flags & FUSE_PASSTHROUGH) && + arg->max_stack_depth > 0 && + arg->max_stack_depth <= FILESYSTEM_MAX_STACK_DEPTH) { + fc->passthrough = 1; + fc->max_stack_depth = arg->max_stack_depth; + fm->sb->s_stack_depth = arg->max_stack_depth; + } } else { ra_pages = fc->max_read / PAGE_SIZE; fc->no_lock = 1; @@ -1367,6 +1391,8 @@ void fuse_send_init(struct fuse_mount *fm) #endif if (fm->fc->auto_submounts) flags |= FUSE_SUBMOUNTS; + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + flags |= FUSE_PASSTHROUGH; ia->in.flags = flags; ia->in.flags2 = flags >> 32; diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c new file mode 100644 index 000000000000..e8639c0a9ac6 --- /dev/null +++ b/fs/fuse/passthrough.c @@ -0,0 +1,30 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * FUSE passthrough to backing file. + * + * Copyright (c) 2023 CTERA Networks. + */ + +#include "fuse_i.h" + +#include <linux/file.h> + +struct fuse_backing *fuse_backing_get(struct fuse_backing *fb) +{ + if (fb && refcount_inc_not_zero(&fb->count)) + return fb; + return NULL; +} + +static void fuse_backing_free(struct fuse_backing *fb) +{ + if (fb->file) + fput(fb->file); + kfree_rcu(fb, rcu); +} + +void fuse_backing_put(struct fuse_backing *fb) +{ + if (fb && refcount_dec_and_test(&fb->count)) + fuse_backing_free(fb); +} diff --git a/fs/fuse/Kconfig b/fs/fuse/Kconfig index 038ed0b9aaa5..8674dbfbe59d 100644 --- a/fs/fuse/Kconfig +++ b/fs/fuse/Kconfig @@ -52,3 +52,14 @@ config FUSE_DAX If you want to allow mounting a Virtio Filesystem with the "dax" option, answer Y. + +config FUSE_PASSTHROUGH + bool "FUSE passthrough operations support" + default y + depends on FUSE_FS + select FS_STACK + help + This allows bypassing FUSE server by mapping specific FUSE operations + to be performed directly on a backing file. + + If you want to allow passthrough operations, answer Y. diff --git a/fs/fuse/Makefile b/fs/fuse/Makefile index b734cc2a5e65..6e0228c6d0cb 100644 --- a/fs/fuse/Makefile +++ b/fs/fuse/Makefile @@ -10,5 +10,6 @@ obj-$(CONFIG_VIRTIO_FS) += virtiofs.o fuse-y := dev.o dir.o file.o inode.o control.o xattr.o acl.o readdir.o ioctl.o fuse-y += iomode.o fuse-$(CONFIG_FUSE_DAX) += dax.o +fuse-$(CONFIG_FUSE_PASSTHROUGH) += passthrough.o virtiofs-y := virtio_fs.o -- 2.39.2