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Subject[PATCH 2/2] afs: Add metadata xattrs
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Add xattrs to allow the user to get/set metadata in lieu of having pioctl()
available. The following xattrs are now available:

(*) afs.cell

The name of the cell in which the vnode's volume resides.

(*) afs.fid

The volume ID, vnode ID and vnode uniquifier of the file as three hex
numbers separated by colons.

(*) afs.volume

The name of the volume in which the vnode resides.

For example:

# getfattr -d -m ".*" /mnt/scratch
getfattr: Removing leading '/' from absolute path names
# file: mnt/scratch
afs.cell="mycell.myorg.org"
afs.fid="10000b:1:1"
afs.volume="scratch"

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/Makefile | 3 +
fs/afs/dir.c | 1
fs/afs/file.c | 1
fs/afs/inode.c | 7 +++
fs/afs/internal.h | 5 ++
fs/afs/mntpt.c | 1
fs/afs/super.c | 1
fs/afs/xattr.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++++++
8 files changed, 138 insertions(+), 2 deletions(-)
create mode 100644 fs/afs/xattr.c

diff --git a/fs/afs/Makefile b/fs/afs/Makefile
index 4f64b95d57bd..095c54165dfd 100644
--- a/fs/afs/Makefile
+++ b/fs/afs/Makefile
@@ -27,6 +27,7 @@ kafs-objs := \
vlocation.o \
vnode.o \
volume.o \
- write.o
+ write.o \
+ xattr.o

obj-$(CONFIG_AFS_FS) := kafs.o
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 949f960337f5..613a77058263 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -61,6 +61,7 @@ const struct inode_operations afs_dir_inode_operations = {
.permission = afs_permission,
.getattr = afs_getattr,
.setattr = afs_setattr,
+ .listxattr = afs_listxattr,
};

const struct dentry_operations afs_fs_dentry_operations = {
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 0d5b8508869b..510cba15fa56 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -46,6 +46,7 @@ const struct inode_operations afs_file_inode_operations = {
.getattr = afs_getattr,
.setattr = afs_setattr,
.permission = afs_permission,
+ .listxattr = afs_listxattr,
};

const struct address_space_operations afs_fs_aops = {
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index aae55dd15108..342316a9e3e0 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -28,6 +28,11 @@ struct afs_iget_data {
struct afs_volume *volume; /* volume on which resides */
};

+static const struct inode_operations afs_symlink_inode_operations = {
+ .get_link = page_get_link,
+ .listxattr = afs_listxattr,
+};
+
/*
* map the AFS file status to the inode member variables
*/
@@ -67,7 +72,7 @@ static int afs_inode_map_status(struct afs_vnode *vnode, struct key *key)
inode->i_fop = &afs_mntpt_file_operations;
} else {
inode->i_mode = S_IFLNK | vnode->status.mode;
- inode->i_op = &page_symlink_inode_operations;
+ inode->i_op = &afs_symlink_inode_operations;
}
inode_nohighmem(inode);
break;
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 4e2556606623..82e16556afea 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -731,6 +731,11 @@ extern int afs_writeback_all(struct afs_vnode *);
extern int afs_flush(struct file *, fl_owner_t);
extern int afs_fsync(struct file *, loff_t, loff_t, int);

+/*
+ * xattr.c
+ */
+extern const struct xattr_handler *afs_xattr_handlers[];
+extern ssize_t afs_listxattr(struct dentry *, char *, size_t);

/*****************************************************************************/
/*
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index bd3b65cde282..690fea9d84c3 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -35,6 +35,7 @@ const struct inode_operations afs_mntpt_inode_operations = {
.lookup = afs_mntpt_lookup,
.readlink = page_readlink,
.getattr = afs_getattr,
+ .listxattr = afs_listxattr,
};

const struct inode_operations afs_autocell_inode_operations = {
diff --git a/fs/afs/super.c b/fs/afs/super.c
index c79633e5cfd8..67680c2d96cf 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -319,6 +319,7 @@ static int afs_fill_super(struct super_block *sb,
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = AFS_FS_MAGIC;
sb->s_op = &afs_super_ops;
+ sb->s_xattr = afs_xattr_handlers;
ret = super_setup_bdi(sb);
if (ret)
return ret;
diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
new file mode 100644
index 000000000000..2830e4f48d85
--- /dev/null
+++ b/fs/afs/xattr.c
@@ -0,0 +1,121 @@
+/* Extended attribute handling for AFS. We use xattrs to get and set metadata
+ * instead of providing pioctl().
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include "internal.h"
+
+static const char afs_xattr_list[] =
+ "afs.cell\0"
+ "afs.fid\0"
+ "afs.volume";
+
+/*
+ * Retrieve a list of the supported xattrs.
+ */
+ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+ if (size == 0)
+ return sizeof(afs_xattr_list);
+ if (size < sizeof(afs_xattr_list))
+ return -ERANGE;
+ memcpy(buffer, afs_xattr_list, sizeof(afs_xattr_list));
+ return sizeof(afs_xattr_list);
+}
+
+/*
+ * Get the name of the cell on which a file resides.
+ */
+static int afs_xattr_get_cell(const struct xattr_handler *handler,
+ struct dentry *dentry,
+ struct inode *inode, const char *name,
+ void *buffer, size_t size)
+{
+ struct afs_vnode *vnode = AFS_FS_I(inode);
+ struct afs_cell *cell = vnode->volume->cell;
+ size_t namelen;
+
+ namelen = strlen(cell->name);
+ if (size == 0)
+ return namelen;
+ if (namelen > size)
+ return -ERANGE;
+ memcpy(buffer, cell->name, size);
+ return namelen;
+}
+
+static const struct xattr_handler afs_xattr_afs_cell_handler = {
+ .name = "afs.cell",
+ .get = afs_xattr_get_cell,
+};
+
+/*
+ * Get the volume ID, vnode ID and vnode uniquifier of a file as a sequence of
+ * hex numbers separated by colons.
+ */
+static int afs_xattr_get_fid(const struct xattr_handler *handler,
+ struct dentry *dentry,
+ struct inode *inode, const char *name,
+ void *buffer, size_t size)
+{
+ struct afs_vnode *vnode = AFS_FS_I(inode);
+ char text[8 + 1 + 8 + 1 + 8 + 1];
+ size_t len;
+
+ len = sprintf(text, "%x:%x:%x",
+ vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
+ if (size == 0)
+ return len;
+ if (len > size)
+ return -ERANGE;
+ memcpy(buffer, text, len);
+ return len;
+}
+
+static const struct xattr_handler afs_xattr_afs_fid_handler = {
+ .name = "afs.fid",
+ .get = afs_xattr_get_fid,
+};
+
+/*
+ * Get the name of the volume on which a file resides.
+ */
+static int afs_xattr_get_volume(const struct xattr_handler *handler,
+ struct dentry *dentry,
+ struct inode *inode, const char *name,
+ void *buffer, size_t size)
+{
+ struct afs_vnode *vnode = AFS_FS_I(inode);
+ const char *volname = vnode->volume->vlocation->vldb.name;
+ size_t namelen;
+
+ namelen = strlen(volname);
+ if (size == 0)
+ return namelen;
+ if (namelen > size)
+ return -ERANGE;
+ memcpy(buffer, volname, size);
+ return namelen;
+}
+
+static const struct xattr_handler afs_xattr_afs_volume_handler = {
+ .name = "afs.volume",
+ .get = afs_xattr_get_volume,
+};
+
+const struct xattr_handler *afs_xattr_handlers[] = {
+ &afs_xattr_afs_cell_handler,
+ &afs_xattr_afs_fid_handler,
+ &afs_xattr_afs_volume_handler,
+ NULL
+};
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