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fuse: Call vfs_get_tree() for submounts

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We recently fixed an infinite loop by setting the SB_BORN flag on
submounts along with the write barrier needed by super_cache_count().
This is the job of vfs_get_tree() and FUSE shouldn't have to care
about the barrier at all.

Split out some code from fuse_dentry_automount() to the dedicated
fuse_get_tree_submount() handler for submounts and call vfs_get_tree().

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Greg Kurz 2021-06-04 18:11:54 +02:00 committed by Miklos Szeredi
parent fe0a7bd81b
commit 266eb3f2fa
2 changed files with 42 additions and 49 deletions
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55
fs/fuse/dir.c
View File

@ -309,12 +309,8 @@ static int fuse_dentry_delete(const struct dentry *dentry)
static struct vfsmount *fuse_dentry_automount(struct path *path)
{
struct fs_context *fsc;
struct fuse_mount *parent_fm = get_fuse_mount_super(path->mnt->mnt_sb);
struct fuse_conn *fc = parent_fm->fc;
struct fuse_mount *fm;
struct vfsmount *mnt;
struct fuse_inode *mp_fi = get_fuse_inode(d_inode(path->dentry));
struct super_block *sb;
int err;
fsc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
@ -323,48 +319,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path)
goto out;
}
err = -ENOMEM;
fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
if (!fm)
/* Pass the FUSE inode of the mount for fuse_get_tree_submount() */
fsc->fs_private = mp_fi;
err = vfs_get_tree(fsc);
if (err)
goto out_put_fsc;
fsc->s_fs_info = fm;
sb = sget_fc(fsc, NULL, set_anon_super_fc);
if (IS_ERR(sb)) {
err = PTR_ERR(sb);
kfree(fm);
goto out_put_fsc;
}
fm->fc = fuse_conn_get(fc);
/* Initialize superblock, making @mp_fi its root */
err = fuse_fill_super_submount(sb, mp_fi);
if (err) {
fuse_conn_put(fc);
kfree(fm);
sb->s_fs_info = NULL;
goto out_put_sb;
}
down_write(&fc->killsb);
list_add_tail(&fm->fc_entry, &fc->mounts);
up_write(&fc->killsb);
sb->s_flags |= SB_ACTIVE;
fsc->root = dget(sb->s_root);
/*
* FIXME: setting SB_BORN requires a write barrier for
* super_cache_count(). We should actually come
* up with a proper ->get_tree() implementation
* for submounts and call vfs_get_tree() to take
* care of the write barrier.
*/
smp_wmb();
sb->s_flags |= SB_BORN;
/* We are done configuring the superblock, so unlock it */
up_write(&sb->s_umount);
up_write(&fsc->root->d_sb->s_umount);
/* Create the submount */
mnt = vfs_create_mount(fsc);
@ -376,12 +339,6 @@ static struct vfsmount *fuse_dentry_automount(struct path *path)
put_fs_context(fsc);
return mnt;
out_put_sb:
/*
* Only jump here when fsc->root is NULL and sb is still locked
* (otherwise put_fs_context() will put the superblock)
*/
deactivate_locked_super(sb);
out_put_fsc:
put_fs_context(fsc);
out:

36
fs/fuse/inode.c
View File

@ -1353,8 +1353,44 @@ int fuse_fill_super_submount(struct super_block *sb,
return 0;
}
/* Filesystem context private data holds the FUSE inode of the mount point */
static int fuse_get_tree_submount(struct fs_context *fsc)
{
struct fuse_mount *fm;
struct fuse_inode *mp_fi = fsc->fs_private;
struct fuse_conn *fc = get_fuse_conn(&mp_fi->inode);
struct super_block *sb;
int err;
fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
if (!fm)
return -ENOMEM;
fsc->s_fs_info = fm;
sb = sget_fc(fsc, NULL, set_anon_super_fc);
if (IS_ERR(sb)) {
kfree(fm);
return PTR_ERR(sb);
}
fm->fc = fuse_conn_get(fc);
/* Initialize superblock, making @mp_fi its root */
err = fuse_fill_super_submount(sb, mp_fi);
if (err) {
fuse_conn_put(fc);
kfree(fm);
sb->s_fs_info = NULL;
deactivate_locked_super(sb);
return err;
}
down_write(&fc->killsb);
list_add_tail(&fm->fc_entry, &fc->mounts);
up_write(&fc->killsb);
sb->s_flags |= SB_ACTIVE;
fsc->root = dget(sb->s_root);
return 0;
}