linux/fs/cifs/dfs_cache.h

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cifs: Add DFS cache routines * Add new dfs_cache.[ch] files * Add new /proc/fs/cifs/dfscache file - dump current cache when read - clear current cache when writing "0" to it * Add delayed_work to periodically refresh cache entries The new interface will be used for caching DFS referrals, as well as supporting client target failover. The DFS cache is a hashtable that maps UNC paths to cache entries. A cache entry contains: - the UNC path it is mapped on - how much the the UNC path the entry consumes - flags - a Time-To-Live after which the entry expires - a list of possible targets (linked lists of UNC paths) - a "hint target" pointing the last known working target or the first target if none were tried. This hint lets cifs.ko remember and try working targets first. * Looking for an entry in the cache is done with dfs_cache_find() - if no valid entries are found, a DFS query is made, stored in the cache and returned - the full target list can be copied and returned to avoid race conditions and looped on with the help with the dfs_cache_tgt_iterator * Updating the target hint to the next target is done with dfs_cache_update_tgthint() These functions have a dfs_cache_noreq_XXX() version that doesn't fetches referrals if no entries are found. These versions don't require the tcp/ses/tcon/cifs_sb parameters as a result. Expired entries cannot be used and since they have a pretty short TTL [1] in order for them to be useful for failover the DFS cache adds a delayed work called periodically to keep them fresh. Since we might not have available connections to issue the referral request when refreshing we need to store volume_info structs with credentials and other needed info to be able to connect to the right server. 1: Windows defaults: 5mn for domain-based referrals, 30mn for regular links Signed-off-by: Paulo Alcantara <palcantara@suse.de> Signed-off-by: Aurelien Aptel <aaptel@suse.com> Signed-off-by: Steve French <stfrench@microsoft.com>
2018-11-15 02:01:21 +08:00
/* SPDX-License-Identifier: GPL-2.0 */
/*
* DFS referral cache routines
*
* Copyright (c) 2018 Paulo Alcantara <palcantara@suse.de>
*/
#ifndef _CIFS_DFS_CACHE_H
#define _CIFS_DFS_CACHE_H
#include <linux/nls.h>
#include <linux/list.h>
#include "cifsglob.h"
struct dfs_cache_tgt_list {
int tl_numtgts;
struct list_head tl_list;
};
struct dfs_cache_tgt_iterator {
char *it_name;
struct list_head it_list;
};
extern int dfs_cache_init(void);
extern void dfs_cache_destroy(void);
extern const struct file_operations dfscache_proc_fops;
extern int dfs_cache_find(const unsigned int xid, struct cifs_ses *ses,
const struct nls_table *nls_codepage, int remap,
const char *path, struct dfs_info3_param *ref,
struct dfs_cache_tgt_list *tgt_list);
extern int dfs_cache_noreq_find(const char *path, struct dfs_info3_param *ref,
struct dfs_cache_tgt_list *tgt_list);
extern int dfs_cache_update_tgthint(const unsigned int xid,
struct cifs_ses *ses,
const struct nls_table *nls_codepage,
int remap, const char *path,
const struct dfs_cache_tgt_iterator *it);
extern int
dfs_cache_noreq_update_tgthint(const char *path,
const struct dfs_cache_tgt_iterator *it);
extern int dfs_cache_get_tgt_referral(const char *path,
const struct dfs_cache_tgt_iterator *it,
struct dfs_info3_param *ref);
extern int dfs_cache_add_vol(struct smb_vol *vol, const char *fullpath);
extern int dfs_cache_update_vol(const char *fullpath,
struct TCP_Server_Info *server);
extern void dfs_cache_del_vol(const char *fullpath);
static inline struct dfs_cache_tgt_iterator *
dfs_cache_get_next_tgt(struct dfs_cache_tgt_list *tl,
struct dfs_cache_tgt_iterator *it)
{
if (!tl || list_empty(&tl->tl_list) || !it ||
list_is_last(&it->it_list, &tl->tl_list))
return NULL;
return list_next_entry(it, it_list);
}
static inline struct dfs_cache_tgt_iterator *
dfs_cache_get_tgt_iterator(struct dfs_cache_tgt_list *tl)
{
if (!tl)
return NULL;
return list_first_entry_or_null(&tl->tl_list,
struct dfs_cache_tgt_iterator,
it_list);
}
static inline void dfs_cache_free_tgts(struct dfs_cache_tgt_list *tl)
{
struct dfs_cache_tgt_iterator *it, *nit;
if (!tl || list_empty(&tl->tl_list))
return;
list_for_each_entry_safe(it, nit, &tl->tl_list, it_list) {
list_del(&it->it_list);
kfree(it->it_name);
kfree(it);
}
tl->tl_numtgts = 0;
}
static inline const char *
dfs_cache_get_tgt_name(const struct dfs_cache_tgt_iterator *it)
{
return it ? it->it_name : NULL;
}
static inline int
dfs_cache_get_nr_tgts(const struct dfs_cache_tgt_list *tl)
{
return tl ? tl->tl_numtgts : 0;
}
#endif /* _CIFS_DFS_CACHE_H */