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54be1f6c1c
* 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>
98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* DFS referral cache routines
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*
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* Copyright (c) 2018 Paulo Alcantara <palcantara@suse.de>
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*/
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#ifndef _CIFS_DFS_CACHE_H
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#define _CIFS_DFS_CACHE_H
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#include <linux/nls.h>
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#include <linux/list.h>
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#include "cifsglob.h"
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struct dfs_cache_tgt_list {
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int tl_numtgts;
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struct list_head tl_list;
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};
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struct dfs_cache_tgt_iterator {
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char *it_name;
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struct list_head it_list;
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};
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extern int dfs_cache_init(void);
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extern void dfs_cache_destroy(void);
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extern const struct file_operations dfscache_proc_fops;
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extern int dfs_cache_find(const unsigned int xid, struct cifs_ses *ses,
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const struct nls_table *nls_codepage, int remap,
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const char *path, struct dfs_info3_param *ref,
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struct dfs_cache_tgt_list *tgt_list);
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extern int dfs_cache_noreq_find(const char *path, struct dfs_info3_param *ref,
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struct dfs_cache_tgt_list *tgt_list);
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extern int dfs_cache_update_tgthint(const unsigned int xid,
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struct cifs_ses *ses,
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const struct nls_table *nls_codepage,
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int remap, const char *path,
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const struct dfs_cache_tgt_iterator *it);
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extern int
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dfs_cache_noreq_update_tgthint(const char *path,
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const struct dfs_cache_tgt_iterator *it);
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extern int dfs_cache_get_tgt_referral(const char *path,
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const struct dfs_cache_tgt_iterator *it,
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struct dfs_info3_param *ref);
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extern int dfs_cache_add_vol(struct smb_vol *vol, const char *fullpath);
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extern int dfs_cache_update_vol(const char *fullpath,
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struct TCP_Server_Info *server);
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extern void dfs_cache_del_vol(const char *fullpath);
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static inline struct dfs_cache_tgt_iterator *
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dfs_cache_get_next_tgt(struct dfs_cache_tgt_list *tl,
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struct dfs_cache_tgt_iterator *it)
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{
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if (!tl || list_empty(&tl->tl_list) || !it ||
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list_is_last(&it->it_list, &tl->tl_list))
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return NULL;
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return list_next_entry(it, it_list);
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}
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static inline struct dfs_cache_tgt_iterator *
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dfs_cache_get_tgt_iterator(struct dfs_cache_tgt_list *tl)
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{
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if (!tl)
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return NULL;
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return list_first_entry_or_null(&tl->tl_list,
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struct dfs_cache_tgt_iterator,
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it_list);
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}
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static inline void dfs_cache_free_tgts(struct dfs_cache_tgt_list *tl)
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{
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struct dfs_cache_tgt_iterator *it, *nit;
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if (!tl || list_empty(&tl->tl_list))
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return;
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list_for_each_entry_safe(it, nit, &tl->tl_list, it_list) {
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list_del(&it->it_list);
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kfree(it->it_name);
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kfree(it);
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}
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tl->tl_numtgts = 0;
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}
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static inline const char *
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dfs_cache_get_tgt_name(const struct dfs_cache_tgt_iterator *it)
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{
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return it ? it->it_name : NULL;
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}
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static inline int
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dfs_cache_get_nr_tgts(const struct dfs_cache_tgt_list *tl)
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{
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return tl ? tl->tl_numtgts : 0;
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}
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#endif /* _CIFS_DFS_CACHE_H */
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