linux/fs/cachefiles/xattr.c
David Howells 32e150037d fscache, cachefiles: Store the volume coherency data
Store the volume coherency data in an xattr and check it when we rebind the
volume.  If it doesn't match the cache volume is moved to the graveyard and
rebuilt anew.

Changes
=======
ver #4:
 - Remove a couple of debugging prints.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/163967164397.1823006.2950539849831291830.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021563138.640689.15851092065380543119.stgit@warthog.procyon.org.uk/ # v4
2022-01-07 13:43:03 +00:00

260 lines
7.2 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* CacheFiles extended attribute management
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/quotaops.h>
#include <linux/xattr.h>
#include <linux/slab.h>
#include "internal.h"
#define CACHEFILES_COOKIE_TYPE_DATA 1
struct cachefiles_xattr {
__be64 object_size; /* Actual size of the object */
__be64 zero_point; /* Size after which server has no data not written by us */
__u8 type; /* Type of object */
__u8 content; /* Content presence (enum cachefiles_content) */
__u8 data[]; /* netfs coherency data */
} __packed;
static const char cachefiles_xattr_cache[] =
XATTR_USER_PREFIX "CacheFiles.cache";
/*
* set the state xattr on a cache file
*/
int cachefiles_set_object_xattr(struct cachefiles_object *object)
{
struct cachefiles_xattr *buf;
struct dentry *dentry;
struct file *file = object->file;
unsigned int len = object->cookie->aux_len;
int ret;
if (!file)
return -ESTALE;
dentry = file->f_path.dentry;
_enter("%x,#%d", object->debug_id, len);
buf = kmalloc(sizeof(struct cachefiles_xattr) + len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
buf->object_size = cpu_to_be64(object->cookie->object_size);
buf->zero_point = 0;
buf->type = CACHEFILES_COOKIE_TYPE_DATA;
buf->content = object->content_info;
if (test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
buf->content = CACHEFILES_CONTENT_DIRTY;
if (len > 0)
memcpy(buf->data, fscache_get_aux(object->cookie), len);
ret = cachefiles_inject_write_error();
if (ret == 0)
ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
buf, sizeof(struct cachefiles_xattr) + len, 0);
if (ret < 0) {
trace_cachefiles_vfs_error(object, file_inode(file), ret,
cachefiles_trace_setxattr_error);
trace_cachefiles_coherency(object, file_inode(file)->i_ino,
buf->content,
cachefiles_coherency_set_fail);
if (ret != -ENOMEM)
cachefiles_io_error_obj(
object,
"Failed to set xattr with error %d", ret);
} else {
trace_cachefiles_coherency(object, file_inode(file)->i_ino,
buf->content,
cachefiles_coherency_set_ok);
}
kfree(buf);
_leave(" = %d", ret);
return ret;
}
/*
* check the consistency between the backing cache and the FS-Cache cookie
*/
int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file)
{
struct cachefiles_xattr *buf;
struct dentry *dentry = file->f_path.dentry;
unsigned int len = object->cookie->aux_len, tlen;
const void *p = fscache_get_aux(object->cookie);
enum cachefiles_coherency_trace why;
ssize_t xlen;
int ret = -ESTALE;
tlen = sizeof(struct cachefiles_xattr) + len;
buf = kmalloc(tlen, GFP_KERNEL);
if (!buf)
return -ENOMEM;
xlen = cachefiles_inject_read_error();
if (xlen == 0)
xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, tlen);
if (xlen != tlen) {
if (xlen < 0)
trace_cachefiles_vfs_error(object, file_inode(file), xlen,
cachefiles_trace_getxattr_error);
if (xlen == -EIO)
cachefiles_io_error_obj(
object,
"Failed to read aux with error %zd", xlen);
why = cachefiles_coherency_check_xattr;
} else if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
why = cachefiles_coherency_check_type;
} else if (memcmp(buf->data, p, len) != 0) {
why = cachefiles_coherency_check_aux;
} else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) {
why = cachefiles_coherency_check_objsize;
} else if (buf->content == CACHEFILES_CONTENT_DIRTY) {
// TODO: Begin conflict resolution
pr_warn("Dirty object in cache\n");
why = cachefiles_coherency_check_dirty;
} else {
why = cachefiles_coherency_check_ok;
ret = 0;
}
trace_cachefiles_coherency(object, file_inode(file)->i_ino,
buf->content, why);
kfree(buf);
return ret;
}
/*
* remove the object's xattr to mark it stale
*/
int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
struct cachefiles_object *object,
struct dentry *dentry)
{
int ret;
ret = cachefiles_inject_remove_error();
if (ret == 0)
ret = vfs_removexattr(&init_user_ns, dentry, cachefiles_xattr_cache);
if (ret < 0) {
trace_cachefiles_vfs_error(object, d_inode(dentry), ret,
cachefiles_trace_remxattr_error);
if (ret == -ENOENT || ret == -ENODATA)
ret = 0;
else if (ret != -ENOMEM)
cachefiles_io_error(cache,
"Can't remove xattr from %lu"
" (error %d)",
d_backing_inode(dentry)->i_ino, -ret);
}
_leave(" = %d", ret);
return ret;
}
/*
* Stick a marker on the cache object to indicate that it's dirty.
*/
void cachefiles_prepare_to_write(struct fscache_cookie *cookie)
{
const struct cred *saved_cred;
struct cachefiles_object *object = cookie->cache_priv;
struct cachefiles_cache *cache = object->volume->cache;
_enter("c=%08x", object->cookie->debug_id);
if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
cachefiles_begin_secure(cache, &saved_cred);
cachefiles_set_object_xattr(object);
cachefiles_end_secure(cache, saved_cred);
}
}
/*
* Set the state xattr on a volume directory.
*/
bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
{
unsigned int len = volume->vcookie->coherency_len;
const void *p = volume->vcookie->coherency;
struct dentry *dentry = volume->dentry;
int ret;
_enter("%x,#%d", volume->vcookie->debug_id, len);
ret = cachefiles_inject_write_error();
if (ret == 0)
ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
p, len, 0);
if (ret < 0) {
trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,
cachefiles_trace_setxattr_error);
trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
cachefiles_coherency_vol_set_fail);
if (ret != -ENOMEM)
cachefiles_io_error(
volume->cache, "Failed to set xattr with error %d", ret);
} else {
trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
cachefiles_coherency_vol_set_ok);
}
_leave(" = %d", ret);
return ret == 0;
}
/*
* Check the consistency between the backing cache and the volume cookie.
*/
int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
{
struct cachefiles_xattr *buf;
struct dentry *dentry = volume->dentry;
unsigned int len = volume->vcookie->coherency_len;
const void *p = volume->vcookie->coherency;
enum cachefiles_coherency_trace why;
ssize_t xlen;
int ret = -ESTALE;
_enter("");
buf = kmalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
xlen = cachefiles_inject_read_error();
if (xlen == 0)
xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, len);
if (xlen != len) {
if (xlen < 0) {
trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,
cachefiles_trace_getxattr_error);
if (xlen == -EIO)
cachefiles_io_error(
volume->cache,
"Failed to read xattr with error %zd", xlen);
}
why = cachefiles_coherency_vol_check_xattr;
} else if (memcmp(buf->data, p, len) != 0) {
why = cachefiles_coherency_vol_check_cmp;
} else {
why = cachefiles_coherency_vol_check_ok;
ret = 0;
}
trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino, why);
kfree(buf);
_leave(" = %d", ret);
return ret;
}