linux_dsm_epyc7002/fs/afs/cache.c
David Howells 27a3ee3a04 afs: Use the vnode ID uniquifier in the cache key not the aux data
AFS vnodes (files) are referenced by a triplet of { volume ID, vnode ID,
uniquifier }.  Currently, kafs is only using the vnode ID as the file key
in the volume fscache index and checking the uniquifier on cookie
acquisition against the contents of the auxiliary data stored in the cache.

Unfortunately, this is subject to a race in which an FS.RemoveFile or
FS.RemoveDir op is issued against the server but the local afs inode isn't
torn down and disposed off before another thread issues something like
FS.CreateFile.  The latter then gets given the vnode ID that just got
removed, but with a new uniquifier and a cookie collision occurs in the
cache because the cookie is only keyed on the vnode ID whereas the inode is
keyed on the vnode ID plus the uniquifier.

Fix this by keying the cookie on the uniquifier in addition to the vnode ID
and dropping the uniquifier from the auxiliary data supplied.

Signed-off-by: David Howells <dhowells@redhat.com>
2018-04-04 13:41:25 +01:00

201 lines
5.2 KiB
C

/* AFS caching stuff
*
* Copyright (C) 2008 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 License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/sched.h>
#include "internal.h"
static uint16_t afs_cell_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t buflen);
static uint16_t afs_volume_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t buflen);
static uint16_t afs_vnode_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t buflen);
static void afs_vnode_cache_get_attr(const void *cookie_netfs_data,
uint64_t *size);
static uint16_t afs_vnode_cache_get_aux(const void *cookie_netfs_data,
void *buffer, uint16_t buflen);
static enum fscache_checkaux afs_vnode_cache_check_aux(void *cookie_netfs_data,
const void *buffer,
uint16_t buflen);
struct fscache_netfs afs_cache_netfs = {
.name = "afs",
.version = 2,
};
struct fscache_cookie_def afs_cell_cache_index_def = {
.name = "AFS.cell",
.type = FSCACHE_COOKIE_TYPE_INDEX,
.get_key = afs_cell_cache_get_key,
};
struct fscache_cookie_def afs_volume_cache_index_def = {
.name = "AFS.volume",
.type = FSCACHE_COOKIE_TYPE_INDEX,
.get_key = afs_volume_cache_get_key,
};
struct fscache_cookie_def afs_vnode_cache_index_def = {
.name = "AFS.vnode",
.type = FSCACHE_COOKIE_TYPE_DATAFILE,
.get_key = afs_vnode_cache_get_key,
.get_attr = afs_vnode_cache_get_attr,
.get_aux = afs_vnode_cache_get_aux,
.check_aux = afs_vnode_cache_check_aux,
};
/*
* set the key for the index entry
*/
static uint16_t afs_cell_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
const struct afs_cell *cell = cookie_netfs_data;
uint16_t klen;
_enter("%p,%p,%u", cell, buffer, bufmax);
klen = strlen(cell->name);
if (klen > bufmax)
return 0;
memcpy(buffer, cell->name, klen);
return klen;
}
/*****************************************************************************/
/*
* set the key for the volume index entry
*/
static uint16_t afs_volume_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
const struct afs_volume *volume = cookie_netfs_data;
struct {
u64 volid;
} __packed key;
_enter("{%u},%p,%u", volume->type, buffer, bufmax);
if (bufmax < sizeof(key))
return 0;
key.volid = volume->vid;
memcpy(buffer, &key, sizeof(key));
return sizeof(key);
}
/*****************************************************************************/
/*
* set the key for the index entry
*/
static uint16_t afs_vnode_cache_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
const struct afs_vnode *vnode = cookie_netfs_data;
struct {
u32 vnode_id;
u32 unique;
u32 vnode_id_ext[2]; /* Allow for a 96-bit key */
} __packed key;
_enter("{%x,%x,%llx},%p,%u",
vnode->fid.vnode, vnode->fid.unique, vnode->status.data_version,
buffer, bufmax);
/* Allow for a 96-bit key */
memset(&key, 0, sizeof(key));
key.vnode_id = vnode->fid.vnode;
key.unique = vnode->fid.unique;
key.vnode_id_ext[0] = 0;
key.vnode_id_ext[1] = 0;
if (sizeof(key) > bufmax)
return 0;
memcpy(buffer, &key, sizeof(key));
return sizeof(key);
}
/*
* provide updated file attributes
*/
static void afs_vnode_cache_get_attr(const void *cookie_netfs_data,
uint64_t *size)
{
const struct afs_vnode *vnode = cookie_netfs_data;
_enter("{%x,%x,%llx},",
vnode->fid.vnode, vnode->fid.unique,
vnode->status.data_version);
*size = vnode->status.size;
}
struct afs_vnode_cache_aux {
u64 data_version;
} __packed;
/*
* provide new auxiliary cache data
*/
static uint16_t afs_vnode_cache_get_aux(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
const struct afs_vnode *vnode = cookie_netfs_data;
struct afs_vnode_cache_aux aux;
_enter("{%x,%x,%Lx},%p,%u",
vnode->fid.vnode, vnode->fid.unique, vnode->status.data_version,
buffer, bufmax);
aux.data_version = vnode->status.data_version;
if (bufmax < sizeof(aux))
return 0;
memcpy(buffer, &aux, sizeof(aux));
return sizeof(aux);
}
/*
* check that the auxiliary data indicates that the entry is still valid
*/
static enum fscache_checkaux afs_vnode_cache_check_aux(void *cookie_netfs_data,
const void *buffer,
uint16_t buflen)
{
struct afs_vnode *vnode = cookie_netfs_data;
struct afs_vnode_cache_aux aux;
_enter("{%x,%x,%llx},%p,%u",
vnode->fid.vnode, vnode->fid.unique, vnode->status.data_version,
buffer, buflen);
memcpy(&aux, buffer, sizeof(aux));
/* check the size of the data is what we're expecting */
if (buflen != sizeof(aux)) {
_leave(" = OBSOLETE [len %hx != %zx]", buflen, sizeof(aux));
return FSCACHE_CHECKAUX_OBSOLETE;
}
if (vnode->status.data_version != aux.data_version) {
_leave(" = OBSOLETE [vers %llx != %llx]",
aux.data_version, vnode->status.data_version);
return FSCACHE_CHECKAUX_OBSOLETE;
}
_leave(" = SUCCESS");
return FSCACHE_CHECKAUX_OKAY;
}