Upon completion of an OPEN, if we're in famfs-mode we do a GET_FMAP to
retrieve and cache up the file-to-dax map in the kernel. If this
succeeds, read/write/mmap are resolved direct-to-dax with no upcalls.
GET_FMAP has a variable-size response payload, and the allocated size
is sent in the in_args[0].size field. If the fmap would overflow the
message, the fuse server sends a reply of size 'sizeof(uint32_t)' which
specifies the size of the fmap message. Then the kernel can realloc a
large enough buffer and try again.
Signed-off-by: John Groves <john@xxxxxxxxxx>
---
fs/fuse/file.c | 84 +++++++++++++++++++++++++++++++++++++++
fs/fuse/fuse_i.h | 36 ++++++++++++++++-
fs/fuse/inode.c | 19 +++++++--
fs/fuse/iomode.c | 2 +-
include/uapi/linux/fuse.h | 18 +++++++++
5 files changed, 154 insertions(+), 5 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 93b82660f0c8..8616fb0a6d61 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -230,6 +230,77 @@ static void fuse_truncate_update_attr(struct inode *inode, struct file *file)
fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
}
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+
+#define FMAP_BUFSIZE 4096
+
+static int
+fuse_get_fmap(struct fuse_mount *fm, struct inode *inode, u64 nodeid)
+{
+ struct fuse_get_fmap_in inarg = { 0 };
+ size_t fmap_bufsize = FMAP_BUFSIZE;
+ ssize_t fmap_size;
+ int retries = 1;
+ void *fmap_buf;
+ int rc;
+
+ FUSE_ARGS(args);
+
+ fmap_buf = kcalloc(1, FMAP_BUFSIZE, GFP_KERNEL);
+ if (!fmap_buf)
+ return -EIO;
+
+ retry_once:
+ inarg.size = fmap_bufsize;
+
+ args.opcode = FUSE_GET_FMAP;
+ args.nodeid = nodeid;
+
+ args.in_numargs = 1;
+ args.in_args[0].size = sizeof(inarg);
+ args.in_args[0].value = &inarg;
+
+ /* Variable-sized output buffer
+ * this causes fuse_simple_request() to return the size of the
+ * output payload
+ */
+ args.out_argvar = true;
+ args.out_numargs = 1;
+ args.out_args[0].size = fmap_bufsize;
+ args.out_args[0].value = fmap_buf;
+
+ /* Send GET_FMAP command */
+ rc = fuse_simple_request(fm, &args);
+ if (rc < 0) {
+ pr_err("%s: err=%d from fuse_simple_request()\n",
+ __func__, rc);
+ return rc;
+ }
+ fmap_size = rc;
+
+ if (retries && fmap_size == sizeof(uint32_t)) {
+ /* fmap size exceeded fmap_bufsize;
+ * actual fmap size returned in fmap_buf;
+ * realloc and retry once
+ */
+ fmap_bufsize = *((uint32_t *)fmap_buf);
+
+ --retries;
+ kfree(fmap_buf);
+ fmap_buf = kcalloc(1, fmap_bufsize, GFP_KERNEL);
+ if (!fmap_buf)
+ return -EIO;
+
+ goto retry_once;
+ }
+
+ /* Will call famfs_file_init_dax() when that gets added */
+
+ kfree(fmap_buf);
+ return 0;
+}
+#endif
+
static int fuse_open(struct inode *inode, struct file *file)
{
struct fuse_mount *fm = get_fuse_mount(inode);
@@ -263,6 +334,19 @@ static int fuse_open(struct inode *inode, struct file *file)
err = fuse_do_open(fm, get_node_id(inode), file, false);
if (!err) {
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ if (fm->fc->famfs_iomap) {
+ if (S_ISREG(inode->i_mode)) {
+ int rc;
+ /* Get the famfs fmap */
+ rc = fuse_get_fmap(fm, inode,
+ get_node_id(inode));
+ if (rc)
+ pr_err("%s: fuse_get_fmap err=%d\n",
+ __func__, rc);
+ }
+ }
+#endif
ff = file->private_data;
err = fuse_finish_open(inode, file);
if (err)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index f4ee61046578..e01d6e5c6e93 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -193,6 +193,10 @@ struct fuse_inode {
/** Reference to backing file in passthrough mode */
struct fuse_backing *fb;
#endif
+
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ void *famfs_meta;
+#endif
};
/** FUSE inode state bits */
@@ -945,6 +949,8 @@ struct fuse_conn {
#endif
#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ struct rw_semaphore famfs_devlist_sem;
+ struct famfs_dax_devlist *dax_devlist;
char *shadow;
#endif
};
@@ -1435,11 +1441,14 @@ void fuse_free_conn(struct fuse_conn *fc);
/* dax.c */
+static inline int fuse_file_famfs(struct fuse_inode *fi); /* forward */
+
/* This macro is used by virtio_fs, but now it also needs to filter for
* "not famfs"
*/
#define FUSE_IS_VIRTIO_DAX(fuse_inode) (IS_ENABLED(CONFIG_FUSE_DAX) \
- && IS_DAX(&fuse_inode->inode))
+ && IS_DAX(&fuse_inode->inode) \
+ && !fuse_file_famfs(fuse_inode))
ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
@@ -1550,4 +1559,29 @@ extern void fuse_sysctl_unregister(void);
#define fuse_sysctl_unregister() do { } while (0)
#endif /* CONFIG_SYSCTL */
+/* famfs.c */
+static inline struct fuse_backing *famfs_meta_set(struct fuse_inode *fi,
+ void *meta)
+{
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ return xchg(&fi->famfs_meta, meta);
+#else
+ return NULL;
+#endif
+}
+
+static inline void famfs_meta_free(struct fuse_inode *fi)
+{
+ /* Stub wil be connected in a subsequent commit */
+}
+
+static inline int fuse_file_famfs(struct fuse_inode *fi)
+{
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ return (READ_ONCE(fi->famfs_meta) != NULL);
+#else
+ return 0;
+#endif
+}
+
#endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index a7e1cf8257b0..b071d16f7d04 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -117,6 +117,9 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
fuse_inode_backing_set(fi, NULL);
+ if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX))
+ famfs_meta_set(fi, NULL);
+
return &fi->inode;
out_free_forget:
@@ -138,6 +141,13 @@ static void fuse_free_inode(struct inode *inode)
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
fuse_backing_put(fuse_inode_backing(fi));
+#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
+ if (S_ISREG(inode->i_mode) && fi->famfs_meta) {
+ famfs_meta_free(fi);
+ famfs_meta_set(fi, NULL);
+ }
+#endif
+
kmem_cache_free(fuse_inode_cachep, fi);
}
@@ -1002,6 +1012,9 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
fuse_backing_files_init(fc);
+ if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX))
+ pr_notice("%s: Kernel is FUSE_FAMFS_DAX capable\n", __func__);
+
INIT_LIST_HEAD(&fc->mounts);
list_add(&fm->fc_entry, &fc->mounts);
fm->fc = fc;
@@ -1036,9 +1049,8 @@ void fuse_conn_put(struct fuse_conn *fc)
}
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
fuse_backing_files_free(fc);
-#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
- kfree(fc->shadow);
-#endif
+ if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX))
+ kfree(fc->shadow);
call_rcu(&fc->rcu, delayed_release);
}
}
@@ -1425,6 +1437,7 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
* those capabilities, they are held here).
*/
fc->famfs_iomap = 1;
+ init_rwsem(&fc->famfs_devlist_sem);
}
} else {
ra_pages = fc->max_read / PAGE_SIZE;
diff --git a/fs/fuse/iomode.c b/fs/fuse/iomode.c
index aec4aecb5d79..443b337b0c05 100644
--- a/fs/fuse/iomode.c
+++ b/fs/fuse/iomode.c
@@ -204,7 +204,7 @@ int fuse_file_io_open(struct file *file, struct inode *inode)
* io modes are not relevant with DAX and with server that does not
* implement open.
*/
- if (FUSE_IS_VIRTIO_DAX(fi) || !ff->args)
+ if (FUSE_IS_VIRTIO_DAX(fi) || fuse_file_famfs(fi) || !ff->args)
return 0;
/*
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 6c384640c79b..dff5aa62543e 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -654,6 +654,10 @@ enum fuse_opcode {
FUSE_TMPFILE = 51,
FUSE_STATX = 52,
+ /* Famfs / devdax opcodes */
+ FUSE_GET_FMAP = 53,
+ FUSE_GET_DAXDEV = 54,
+
/* CUSE specific operations */
CUSE_INIT = 4096,
@@ -888,6 +892,16 @@ struct fuse_access_in {
uint32_t padding;
};
+struct fuse_get_fmap_in {
+ uint32_t size;
+ uint32_t padding;
+};
+
+struct fuse_get_fmap_out {
+ uint32_t size;
+ uint32_t padding;
+};
+
struct fuse_init_in {
uint32_t major;
uint32_t minor;
@@ -1284,4 +1298,8 @@ struct fuse_uring_cmd_req {
uint8_t padding[6];
};
+/* Famfs fmap message components */
+
+#define FAMFS_FMAP_MAX 32768 /* Largest supported fmap message */
+
#endif /* _LINUX_FUSE_H */
--
2.49.0
