Add unprivileged ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF which
returns ROOT_REF information of the subvolume containing this inode.
The min id of root ref's subvolume to be searched is specified by
min_id in struct btrfs_ioctl_get_subvol_rootref_args.
If there are more root refs than BTRFS_MAX_ROOTREF_BUFFER_NUM,
this ioctl sets min_id to the last searched root ref's subvolid + 1
and return -EOVERFLOW. Therefore the caller can just call this ioctl
again without changing the argument to continue search.
Signed-off-by: Tomohiro Misono <misono.tomoh...@jp.fujitsu.com>
---
fs/btrfs/ioctl.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/btrfs.h | 16 ++++++++
2 files changed, 107 insertions(+)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 852421ac81cd..816a3eb60020 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2425,6 +2425,95 @@ static noinline int btrfs_ioctl_get_subvol_info(struct
file *file,
return ret;
}
+/* Returns ROOT_REF information of the subvolume contining this inode. */
+static noinline int btrfs_ioctl_get_subvol_rootref(struct file *file,
+ void __user *argp)
+{
+ struct btrfs_ioctl_get_subvol_rootref_args __user *rootrefs;
+ struct btrfs_root_ref *rref;
+ struct btrfs_root *root;
+ struct btrfs_path *path;
+ struct btrfs_key key;
+
+ struct extent_buffer *l;
+ int slot;
+
+ struct inode *inode;
+ int i, nritems;
+ int ret;
+ u64 objectid;
+ u8 found;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ rootrefs = memdup_user(argp, sizeof(*rootrefs));
+ if (!rootrefs) {
+ btrfs_free_path(path);
+ return -ENOMEM;
+ }
+
+ inode = file_inode(file);
+ root = BTRFS_I(inode)->root->fs_info->tree_root;
+ objectid = BTRFS_I(inode)->root->root_key.objectid;
+
+ key.objectid = objectid;
+ key.type = BTRFS_ROOT_REF_KEY;
+ key.offset = rootrefs->min_id;
+ found = 0;
+ while (1) {
+ ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ if (ret < 0)
+ goto out;
+
+ l = path->nodes[0];
+ slot = path->slots[0];
+ nritems = btrfs_header_nritems(l);
+ if (nritems - slot == 0) {
+ ret = 0;
+ goto out;
+ }
+
+ for (i = slot; i < nritems; i++) {
+ btrfs_item_key_to_cpu(l, &key, i);
+ if (key.objectid != objectid ||
+ key.type != BTRFS_ROOT_REF_KEY) {
+ ret = 0;
+ goto out;
+ }
+
+ if (found == BTRFS_MAX_ROOTREF_BUFFER_NUM) {
+ /* update min_id for next search */
+ rootrefs->min_id = key.offset;
+ ret = -EOVERFLOW;
+ goto out;
+ }
+
+ rref = btrfs_item_ptr(l, i, struct btrfs_root_ref);
+ rootrefs->rootref[found].subvolid = key.offset;
+ rootrefs->rootref[found].dirid =
+ btrfs_root_ref_dirid(l, rref);
+ found++;
+ }
+
+ btrfs_release_path(path);
+ key.offset++;
+ }
+
+out:
+ if (!ret || ret == -EOVERFLOW) {
+ rootrefs->num_items = found;
+ if (copy_to_user(argp, rootrefs, sizeof(*rootrefs)))
+ ret = -EFAULT;
+ }
+
+ btrfs_free_path(path);
+ kfree(rootrefs);
+
+ return ret;
+}
+
static noinline int btrfs_ioctl_snap_destroy(struct file *file,
void __user *arg)
{
@@ -5781,6 +5870,8 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_set_features(file, argp);
case BTRFS_IOC_GET_SUBVOL_INFO:
return btrfs_ioctl_get_subvol_info(file, argp);
+ case BTRFS_IOC_GET_SUBVOL_ROOTREF:
+ return btrfs_ioctl_get_subvol_rootref(file, argp);
}
return -ENOTTY;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index ed053852c71f..82c88d52d6e6 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -774,6 +774,20 @@ struct btrfs_ioctl_get_subvol_info_args {
__u64 reserved[8];
};
+#define BTRFS_MAX_ROOTREF_BUFFER_NUM 255
+struct btrfs_ioctl_get_subvol_rootref_args {
+ /* in/out, min id of rootref's subvolid to be searched */
+ __u64 min_id;
+ /* out */
+ struct {
+ __u64 subvolid;
+ __u64 dirid;
+ } rootref[BTRFS_MAX_ROOTREF_BUFFER_NUM];
+ /* out, number of found items */
+ __u8 num_items;
+ __u8 align[7];
+};
+
/* Error codes as returned by the kernel */
enum btrfs_err_code {
BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
@@ -894,5 +908,7 @@ enum btrfs_err_code {
struct btrfs_ioctl_logical_ino_args)
#define BTRFS_IOC_GET_SUBVOL_INFO _IOR(BTRFS_IOCTL_MAGIC, 60, \
struct btrfs_ioctl_get_subvol_info_args)
+#define BTRFS_IOC_GET_SUBVOL_ROOTREF _IOWR(BTRFS_IOCTL_MAGIC, 61, \
+ struct btrfs_ioctl_get_subvol_rootref_args)
#endif /* _UAPI_LINUX_BTRFS_H */
--
2.14.3
--
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