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Subject[PATCH -V14 02/11] vfs: Add name to file handle conversion support
Date
This patch add a new superblock field unsigned char s_uuid[16]
to store UUID mapping for the file system. The s_uuid[16] is used to
identify the file system apart of file_handle

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/open.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 11 ++++
include/linux/syscalls.h | 3 +
3 files changed, 142 insertions(+), 0 deletions(-)
diff --git a/fs/open.c b/fs/open.c
index 5463266..43ac798 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -29,6 +29,7 @@
#include <linux/falloc.h>
#include <linux/fs_struct.h>
#include <linux/ima.h>
+#include <linux/exportfs.h>

#include "internal.h"

@@ -1040,3 +1041,130 @@ int nonseekable_open(struct inode *inode, struct file *filp)
}

EXPORT_SYMBOL(nonseekable_open);
+
+#ifdef CONFIG_EXPORTFS
+/* limit the handle size to some value */
+#define MAX_HANDLE_SZ 4096
+static long do_sys_name_to_handle(struct path *path,
+ struct file_handle __user *ufh)
+{
+ long retval;
+ int handle_size;
+ struct super_block *sb;
+ struct file_handle f_handle;
+ struct file_handle *handle = NULL;
+
+ if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+ retval = -EFAULT;
+ goto err_out;
+ }
+ if (f_handle.handle_size > MAX_HANDLE_SZ) {
+ retval = -EINVAL;
+ goto err_out;
+ }
+ handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+ GFP_KERNEL);
+ if (!handle) {
+ retval = -ENOMEM;
+ goto err_out;
+ }
+
+ /* convert handle size to multiple of sizeof(u32) */
+ handle_size = f_handle.handle_size >> 2;
+
+ /* we ask for a non connected handle */
+ retval = exportfs_encode_fh(path->dentry,
+ (struct fid *)handle->f_handle,
+ &handle_size, 0);
+ /* convert handle size to bytes */
+ handle_size *= sizeof(u32);
+ handle->handle_type = retval;
+ handle->handle_size = handle_size;
+ if (handle_size <= f_handle.handle_size) {
+ /* get the uuid */
+ sb = path->mnt->mnt_sb;
+ memcpy(handle->fs_uuid,
+ sb->s_uuid,
+ sizeof(handle->fs_uuid));
+ retval = 0;
+ } else {
+ /*
+ * set the handle_size to zero so we copy only
+ * non variable part of the file_handle
+ */
+ handle_size = 0;
+ retval = -EOVERFLOW;
+ }
+ if (copy_to_user(ufh, handle,
+ sizeof(struct file_handle) + handle_size))
+ retval = -EFAULT;
+
+ kfree(handle);
+err_out:
+ 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
+ * @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_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name,
+ struct file_handle __user *, handle, int, flag)
+{
+
+ int follow;
+ long ret = -EINVAL;
+ struct path path, *pp;
+ struct file *file = NULL;
+
+ if ((flag & ~AT_SYMLINK_FOLLOW) != 0)
+ goto err_out;
+
+ if (name == NULL && dfd != AT_FDCWD) {
+ file = fget(dfd);
+ if (file) {
+ pp = &file->f_path;
+ ret = 0;
+ } else
+ ret = -EBADF;
+ } else {
+ follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+ ret = user_path_at(dfd, name, follow, &path);
+ pp = &path;
+ }
+ if (ret)
+ goto err_out;
+ /*
+ * We need t make sure wether the file system
+ * support decoding of the file handle
+ */
+ if (!pp->mnt->mnt_sb->s_export_op ||
+ !pp->mnt->mnt_sb->s_export_op->fh_to_dentry) {
+ ret = -EOPNOTSUPP;
+ goto out_path;
+ }
+ ret = do_sys_name_to_handle(pp, handle);
+
+out_path:
+ if (file)
+ fput(file);
+ else
+ path_put(&path);
+err_out:
+ return ret;
+}
+#else
+SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name,
+ struct file_handle __user *, handle, int, flag)
+{
+ return -ENOSYS;
+}
+#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 471e1ff..ebc0f98 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -949,6 +949,16 @@ struct file {
unsigned long f_mnt_write_state;
#endif
};
+
+struct file_handle {
+ int handle_size;
+ int handle_type;
+ /* File system UUID identifier */
+ u8 fs_uuid[16];
+ /* file identifier */
+ unsigned char f_handle[0];
+};
+
extern spinlock_t files_lock;
#define file_list_lock() spin_lock(&files_lock);
#define file_list_unlock() spin_unlock(&files_lock);
@@ -1357,6 +1367,7 @@ struct super_block {
wait_queue_head_t s_wait_unfrozen;

char s_id[32]; /* Informational name */
+ u8 s_uuid[16]; /* UUID */

void *s_fs_info; /* Filesystem private info */
fmode_t s_mode;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 7f614ce..4d4e922 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -61,6 +61,7 @@ struct robust_list_head;
struct getcpu_cache;
struct old_linux_dirent;
struct perf_event_attr;
+struct file_handle;

#include <linux/types.h>
#include <linux/aio_abi.h>
@@ -823,5 +824,7 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
unsigned long fd, unsigned long pgoff);
asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
+asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
+ struct file_handle __user *handle, int flag);

#endif
--
1.7.1.331.ga5080


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