Btrfs: Add mount into directory support
Modified form of original patch from Christoph Hellwig to make btrfs mount into the default subvolume by default. mount /dev/somedevice:subvolumename to get other subvolumes or mount /dev/somedevice:. to get the root Signed-off-by: Chris Mason <chris.mason@oracle.com>
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1b4ab1bb4b
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125
fs/btrfs/super.c
125
fs/btrfs/super.c
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@ -16,6 +16,7 @@
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* Boston, MA 021110-1307, USA.
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*/
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#include <linux/blkdev.h>
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#include <linux/module.h>
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#include <linux/buffer_head.h>
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#include <linux/fs.h>
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@ -26,6 +27,7 @@
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#include <linux/string.h>
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#include <linux/smp_lock.h>
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#include <linux/backing-dev.h>
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#include <linux/mount.h>
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#include <linux/mpage.h>
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#include <linux/swap.h>
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#include <linux/writeback.h>
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@ -145,11 +147,126 @@ static void btrfs_write_super(struct super_block *sb)
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sb->s_dirt = 0;
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}
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static int btrfs_get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data, struct vfsmount *mnt)
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/*
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* This is almost a copy of get_sb_bdev in fs/super.c.
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* We need the local copy to allow direct mounting of
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* subvolumes, but this could be easily integrated back
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* into the generic version. --hch
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*/
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/* start copy & paste */
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static int set_bdev_super(struct super_block *s, void *data)
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{
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return get_sb_bdev(fs_type, flags, dev_name, data,
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btrfs_fill_super, mnt);
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s->s_bdev = data;
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s->s_dev = s->s_bdev->bd_dev;
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return 0;
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}
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static int test_bdev_super(struct super_block *s, void *data)
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{
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return (void *)s->s_bdev == data;
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}
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int btrfs_get_sb_bdev(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data,
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int (*fill_super)(struct super_block *, void *, int),
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struct vfsmount *mnt, const char *subvol)
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{
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struct block_device *bdev = NULL;
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struct super_block *s;
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struct dentry *root;
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int error = 0;
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bdev = open_bdev_excl(dev_name, flags, fs_type);
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if (IS_ERR(bdev))
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return PTR_ERR(bdev);
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/*
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* once the super is inserted into the list by sget, s_umount
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* will protect the lockfs code from trying to start a snapshot
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* while we are mounting
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*/
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down(&bdev->bd_mount_sem);
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s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
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up(&bdev->bd_mount_sem);
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if (IS_ERR(s))
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goto error_s;
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if (s->s_root) {
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if ((flags ^ s->s_flags) & MS_RDONLY) {
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up_write(&s->s_umount);
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deactivate_super(s);
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error = -EBUSY;
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goto error_bdev;
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}
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close_bdev_excl(bdev);
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} else {
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char b[BDEVNAME_SIZE];
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s->s_flags = flags;
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strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
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sb_set_blocksize(s, block_size(bdev));
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error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
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if (error) {
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up_write(&s->s_umount);
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deactivate_super(s);
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goto error;
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}
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s->s_flags |= MS_ACTIVE;
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}
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if (subvol) {
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root = lookup_one_len(subvol, s->s_root, strlen(subvol));
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if (IS_ERR(root)) {
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up_write(&s->s_umount);
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deactivate_super(s);
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error = PTR_ERR(root);
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goto error;
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}
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if (!root->d_inode) {
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dput(root);
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up_write(&s->s_umount);
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deactivate_super(s);
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error = -ENXIO;
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goto error;
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}
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} else {
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root = dget(s->s_root);
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}
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mnt->mnt_sb = s;
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mnt->mnt_root = root;
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return 0;
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error_s:
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error = PTR_ERR(s);
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error_bdev:
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close_bdev_excl(bdev);
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error:
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return error;
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}
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/* end copy & paste */
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static int btrfs_get_sb(struct file_system_type *fs_type,
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int flags, const char *identifier, void *data, struct vfsmount *mnt)
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{
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int ret;
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char *_identifier = kstrdup(identifier, GFP_KERNEL);
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char *subvol_name;
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const char *dev_name;
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subvol_name = _identifier;
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dev_name = strsep(&subvol_name, ":");
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if (!dev_name)
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return -ENOMEM;
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ret = btrfs_get_sb_bdev(fs_type, flags, dev_name, data,
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btrfs_fill_super, mnt,
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subvol_name ? subvol_name : "default");
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kfree(_identifier);
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return ret;
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}
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static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
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