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Subject[PATCH -V9 2/9] 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/exportfs/expfs.c | 2 +-
fs/open.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 15 +++++++++
3 files changed, 98 insertions(+), 1 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfee0f0..d103c31 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -352,7 +352,7 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
const struct export_operations *nop = dentry->d_sb->s_export_op;
int error;

- if (nop->encode_fh)
+ if (nop && nop->encode_fh)
error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
else
error = export_encode_fh(dentry, fid, max_len, connectable);
diff --git a/fs/open.c b/fs/open.c
index 74e5cd9..51aa494 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
#include <linux/falloc.h>
#include <linux/fs_struct.h>
#include <linux/ima.h>
+#include <linux/exportfs.h>

#include "internal.h"

@@ -1206,3 +1207,84 @@ int nonseekable_open(struct inode *inode, struct file *filp)
}

EXPORT_SYMBOL(nonseekable_open);
+
+/* 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)
+{
+ int 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;
+ }
+ handle_size = f_handle.handle_size;
+
+ /* 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->fsid.uuid,
+ sb->s_uuid,
+ sizeof(handle->fsid.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;
+}
+
+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;
+
+ if ((flag & ~AT_SYMLINK_FOLLOW) != 0)
+ goto err_out;
+
+ follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+ ret = user_path_at(dfd, name, follow, &path);
+ if (ret)
+ goto err_out;
+ ret = do_sys_name_to_handle(&path, handle);
+ path_put(&path);
+err_out:
+ /* avoid REGPARM breakage on x86: */
+ asmlinkage_protect(4, ret, dfd, name, handle, flag);
+ return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 44f35ae..961392c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -948,6 +948,20 @@ struct file {
unsigned long f_mnt_write_state;
#endif
};
+
+struct uuid {
+ unsigned char uuid[16];
+};
+
+struct file_handle {
+ int handle_size;
+ int handle_type;
+ /* File system identifier */
+ struct uuid fsid;
+ /* 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);
@@ -1358,6 +1372,7 @@ struct super_block {
wait_queue_head_t s_wait_unfrozen;

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

void *s_fs_info; /* Filesystem private info */
fmode_t s_mode;
--
1.7.1.78.g212f0


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