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Subject[PATCH v4 09/16] fuse: extract fuse_fill_super_common()
Date
From: Stefan Hajnoczi <stefanha@redhat.com>

fuse_fill_super() includes code to process the fd= option and link the
struct fuse_dev to the fd's struct file. In virtio-fs there is no file
descriptor because /dev/fuse is not used.

This patch extracts fuse_fill_super_common() so that both classic fuse and
virtio-fs can share the code to initialize a mount.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/fuse/fuse_i.h | 27 ++++++++++
fs/fuse/inode.c | 133 +++++++++++++++++++++++------------------------
2 files changed, 91 insertions(+), 69 deletions(-)

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6533be37873f..d0c8f131fb5d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -504,6 +504,26 @@ struct fuse_dev {
struct list_head entry;
};

+struct fuse_fs_context {
+ int fd;
+ unsigned int rootmode;
+ kuid_t user_id;
+ kgid_t group_id;
+ bool is_bdev:1;
+ bool fd_present:1;
+ bool rootmode_present:1;
+ bool user_id_present:1;
+ bool group_id_present:1;
+ bool default_permissions:1;
+ bool allow_other:1;
+ unsigned int max_read;
+ unsigned int blksize;
+ const char *subtype;
+
+ /* fuse_dev pointer to fill in, should contain NULL on entry */
+ void **fudptr;
+};
+
/**
* A Fuse connection.
*
@@ -1000,6 +1020,13 @@ struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc);
void fuse_dev_free(struct fuse_dev *fud);
void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req);

+/**
+ * Fill in superblock and initialize fuse connection
+ * @sb: partially-initialized superblock to fill in
+ * @ctx: mount context
+ */
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx);
+
/**
* Add connection to control filesystem
*/
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 31cf0c47da13..048816c95b69 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -64,23 +64,6 @@ MODULE_PARM_DESC(max_user_congthresh,
static struct file_system_type fuseblk_fs_type;
#endif

-struct fuse_fs_context {
- const char *subtype;
- bool is_bdev;
- int fd;
- unsigned rootmode;
- kuid_t user_id;
- kgid_t group_id;
- unsigned fd_present:1;
- unsigned rootmode_present:1;
- unsigned user_id_present:1;
- unsigned group_id_present:1;
- unsigned default_permissions:1;
- unsigned allow_other:1;
- unsigned max_read;
- unsigned blksize;
-};
-
struct fuse_forget_link *fuse_alloc_forget(void)
{
return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL);
@@ -1083,17 +1066,13 @@ void fuse_dev_free(struct fuse_dev *fud)
}
EXPORT_SYMBOL_GPL(fuse_dev_free);

-static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
{
- struct fuse_fs_context *ctx = fsc->fs_private;
struct fuse_dev *fud;
- struct fuse_conn *fc;
+ struct fuse_conn *fc = get_fuse_conn_super(sb);
struct inode *root;
- struct file *file;
struct dentry *root_dentry;
- struct fuse_req *init_req;
int err;
- int is_bdev = sb->s_bdev != NULL;

err = -EINVAL;
if (sb->s_flags & SB_MANDLOCK)
@@ -1101,7 +1080,7 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)

sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);

- if (is_bdev) {
+ if (ctx->is_bdev) {
#ifdef CONFIG_BLOCK
err = -EINVAL;
if (!sb_set_blocksize(sb, ctx->blksize))
@@ -1124,19 +1103,6 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
if (sb->s_user_ns != &init_user_ns)
sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;

- file = fget(ctx->fd);
- err = -EINVAL;
- if (!file)
- goto err;
-
- /*
- * Require mount to happen from the same user namespace which
- * opened /dev/fuse to prevent potential attacks.
- */
- if (file->f_op != &fuse_dev_operations ||
- file->f_cred->user_ns != sb->s_user_ns)
- goto err_fput;
-
/*
* If we are not in the initial user namespace posix
* acls must be translated.
@@ -1144,17 +1110,9 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
if (sb->s_user_ns != &init_user_ns)
sb->s_xattr = fuse_no_acl_xattr_handlers;

- fc = kmalloc(sizeof(*fc), GFP_KERNEL);
- err = -ENOMEM;
- if (!fc)
- goto err_fput;
-
- fuse_conn_init(fc, sb->s_user_ns);
- fc->release = fuse_free_conn;
-
fud = fuse_dev_alloc(fc);
if (!fud)
- goto err_put_conn;
+ goto err;

fc->dev = sb->s_dev;
fc->sb = sb;
@@ -1173,9 +1131,6 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
fc->group_id = ctx->group_id;
fc->max_read = max_t(unsigned, 4096, ctx->max_read);

- /* Used by get_root_inode() */
- sb->s_fs_info = fc;
-
err = -ENOMEM;
root = fuse_get_root_inode(sb, ctx->rootmode);
sb->s_d_op = &fuse_root_dentry_operations;
@@ -1185,20 +1140,15 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
/* Root dentry doesn't have .d_revalidate */
sb->s_d_op = &fuse_dentry_operations;

- init_req = fuse_request_alloc(0);
- if (!init_req)
- goto err_put_root;
- __set_bit(FR_BACKGROUND, &init_req->flags);
-
- if (is_bdev) {
+ if (ctx->is_bdev) {
fc->destroy_req = fuse_request_alloc(0);
if (!fc->destroy_req)
- goto err_free_init_req;
+ goto err_put_root;
}

mutex_lock(&fuse_mutex);
err = -EINVAL;
- if (file->private_data)
+ if (*ctx->fudptr)
goto err_unlock;

err = fuse_ctl_add_conn(fc);
@@ -1207,30 +1157,75 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)

list_add_tail(&fc->entry, &fuse_conn_list);
sb->s_root = root_dentry;
- file->private_data = fud;
+ *ctx->fudptr = fud;
mutex_unlock(&fuse_mutex);
- /*
- * atomic_dec_and_test() in fput() provides the necessary
- * memory barrier for file->private_data to be visible on all
- * CPUs after this
- */
- fput(file);
-
- fuse_send_init(fc, init_req);
-
return 0;

err_unlock:
mutex_unlock(&fuse_mutex);
- err_free_init_req:
- fuse_request_free(init_req);
err_put_root:
dput(root_dentry);
err_dev_free:
fuse_dev_free(fud);
+ err:
+ return err;
+}
+EXPORT_SYMBOL_GPL(fuse_fill_super_common);
+
+static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
+{
+ struct fuse_fs_context *ctx = fsc->fs_private;
+ struct file *file;
+ int err;
+ struct fuse_req *init_req;
+ struct fuse_conn *fc;
+
+ err = -EINVAL;
+ file = fget(ctx->fd);
+ if (!file)
+ goto err;
+
+ /*
+ * Require mount to happen from the same user namespace which
+ * opened /dev/fuse to prevent potential attacks.
+ */
+ if ((file->f_op != &fuse_dev_operations) ||
+ (file->f_cred->user_ns != sb->s_user_ns))
+ goto err_fput;
+
+ init_req = fuse_request_alloc(0);
+ if (!init_req)
+ goto err_fput;
+ __set_bit(FR_BACKGROUND, &init_req->flags);
+
+ ctx->fudptr = &file->private_data;
+
+ fc = kmalloc(sizeof(*fc), GFP_KERNEL);
+ err = -ENOMEM;
+ if (!fc)
+ goto err_free_init_req;
+
+ fuse_conn_init(fc, sb->s_user_ns);
+ fc->release = fuse_free_conn;
+ sb->s_fs_info = fc;
+
+ err = fuse_fill_super_common(sb, ctx);
+ if (err)
+ goto err_put_conn;
+ /*
+ * atomic_dec_and_test() in fput() provides the necessary
+ * memory barrier for file->private_data to be visible on all
+ * CPUs after this
+ */
+ fput(file);
+ fuse_send_init(get_fuse_conn_super(sb), init_req);
+ return 0;
+
err_put_conn:
fuse_conn_put(fc);
sb->s_fs_info = NULL;
+ err_free_init_req:
+ fuse_request_free(init_req);
err_fput:
fput(file);
err:
--
2.21.0
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