btrfs: new ioctl TREE_SEARCH_V2

This new ioctl call allows the user to supply a buffer of varying size in which
a tree search can store its results. This is much more flexible if you want to
receive items which are larger than the current fixed buffer of 3992 bytes or
if you want to fetch more items at once. Items larger than this buffer are for
example some of the type EXTENT_CSUM.

Signed-off-by: Gerhard Heift <Gerhard@Heift.Name>
Signed-off-by: Chris Mason <clm@fb.com>
Acked-by: David Sterba <dsterba@suse.cz>

1 files changed, 41 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 393a543a519e..6ea15469c63f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2172,6 +2172,45 @@ static noinline int btrfs_ioctl_tree_search(struct file *file,
         return ret;
 }
 
+static noinline int btrfs_ioctl_tree_search_v2(struct file *file,
+                                               void __user *argp)
+{
+        struct btrfs_ioctl_search_args_v2 __user *uarg;
+        struct btrfs_ioctl_search_args_v2 args;
+        struct inode *inode;
+        int ret;
+        size_t buf_size;
+        const size_t buf_limit = 16 * 1024 * 1024;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        /* copy search header and buffer size */
+        uarg = (struct btrfs_ioctl_search_args_v2 __user *)argp;
+        if (copy_from_user(&args, uarg, sizeof(args)))
+                return -EFAULT;
+
+        buf_size = args.buf_size;
+
+        if (buf_size < sizeof(struct btrfs_ioctl_search_header))
+                return -EOVERFLOW;
+
+        /* limit result size to 16MB */
+        if (buf_size > buf_limit)
+                buf_size = buf_limit;
+
+        inode = file_inode(file);
+        ret = search_ioctl(inode, &args.key, &buf_size,
+                           (char *)(&uarg->buf[0]));
+        if (ret == 0 && copy_to_user(&uarg->key, &args.key, sizeof(args.key)))
+                ret = -EFAULT;
+        else if (ret == -EOVERFLOW &&
+                copy_to_user(&uarg->buf_size, &buf_size, sizeof(buf_size)))
+                ret = -EFAULT;
+
+        return ret;
+}
+
 /*
  * Search INODE_REFs to identify path name of 'dirid' directory
  * in a 'tree_id' tree. and sets path name to 'name'.
@@ -5252,6 +5291,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_trans_end(file);
         case BTRFS_IOC_TREE_SEARCH:
                 return btrfs_ioctl_tree_search(file, argp);
+        case BTRFS_IOC_TREE_SEARCH_V2:
+                return btrfs_ioctl_tree_search_v2(file, argp);
         case BTRFS_IOC_INO_LOOKUP:
                 return btrfs_ioctl_ino_lookup(file, argp);
         case BTRFS_IOC_INO_PATHS: