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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2011-01-29 18:43:26 +0530
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-15 02:21:37 -0400
commit990d6c2d7aee921e3bce22b2d6a750fd552262be (patch)
treeaf273c4bfbfd0342d39d05d5a017382eb32a7538 /fs/fhandle.c
parentf52e0c11305aa09ed56cad97ffc8f0cdc3d78b5d (diff)
downloadlinaro-lsk-990d6c2d7aee921e3bce22b2d6a750fd552262be.tar.gz
vfs: Add name to file handle conversion support
The syscall also return mount id which can be used to lookup file system specific information such as uuid in /proc/<pid>/mountinfo Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/fhandle.c')
-rw-r--r--fs/fhandle.c107
1 files changed, 107 insertions, 0 deletions
diff --git a/fs/fhandle.c b/fs/fhandle.c
new file mode 100644
index 00000000000..9f79e743a84
--- /dev/null
+++ b/fs/fhandle.c
@@ -0,0 +1,107 @@
+#include <linux/syscalls.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/exportfs.h>
+#include <asm/uaccess.h>
+#include "internal.h"
+
+static long do_sys_name_to_handle(struct path *path,
+ struct file_handle __user *ufh,
+ int __user *mnt_id)
+{
+ long retval;
+ struct file_handle f_handle;
+ int handle_dwords, handle_bytes;
+ struct file_handle *handle = NULL;
+
+ /*
+ * We need t make sure wether the file system
+ * support decoding of the file handle
+ */
+ if (!path->mnt->mnt_sb->s_export_op ||
+ !path->mnt->mnt_sb->s_export_op->fh_to_dentry)
+ return -EOPNOTSUPP;
+
+ if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
+ return -EFAULT;
+
+ if (f_handle.handle_bytes > MAX_HANDLE_SZ)
+ return -EINVAL;
+
+ handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
+ GFP_KERNEL);
+ if (!handle)
+ return -ENOMEM;
+
+ /* convert handle size to multiple of sizeof(u32) */
+ handle_dwords = f_handle.handle_bytes >> 2;
+
+ /* we ask for a non connected handle */
+ retval = exportfs_encode_fh(path->dentry,
+ (struct fid *)handle->f_handle,
+ &handle_dwords, 0);
+ handle->handle_type = retval;
+ /* convert handle size to bytes */
+ handle_bytes = handle_dwords * sizeof(u32);
+ handle->handle_bytes = handle_bytes;
+ if ((handle->handle_bytes > f_handle.handle_bytes) ||
+ (retval == 255) || (retval == -ENOSPC)) {
+ /* As per old exportfs_encode_fh documentation
+ * we could return ENOSPC to indicate overflow
+ * But file system returned 255 always. So handle
+ * both the values
+ */
+ /*
+ * set the handle size to zero so we copy only
+ * non variable part of the file_handle
+ */
+ handle_bytes = 0;
+ retval = -EOVERFLOW;
+ } else
+ retval = 0;
+ /* copy the mount id */
+ if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) ||
+ copy_to_user(ufh, handle,
+ sizeof(struct file_handle) + handle_bytes))
+ retval = -EFAULT;
+ kfree(handle);
+ return retval;
+}
+
+/**
+ * sys_name_to_handle_at: convert name to handle
+ * @dfd: directory relative to which name is interpreted if not absolute
+ * @name: name that should be converted to handle.
+ * @handle: resulting file handle
+ * @mnt_id: mount id of the file system containing the file
+ * @flag: flag value to indicate whether to follow symlink or not
+ *
+ * @handle->handle_size indicate the space available to store the
+ * variable part of the file handle in bytes. If there is not
+ * enough space, the field is updated to return the minimum
+ * value required.
+ */
+SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
+ struct file_handle __user *, handle, int __user *, mnt_id,
+ int, flag)
+{
+ struct path path;
+ int lookup_flags;
+ int err;
+
+ if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+
+ lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+ if (flag & AT_EMPTY_PATH)
+ lookup_flags |= LOOKUP_EMPTY;
+ err = user_path_at(dfd, name, lookup_flags, &path);
+ if (!err) {
+ err = do_sys_name_to_handle(&path, handle, mnt_id);
+ path_put(&path);
+ }
+ return err;
+}