release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/s390/scsi/zfcp_reqlist.h

   1 /*
   2  * zfcp device driver
   3  *
   4  * Data structure and helper functions for tracking pending FSF
   5  * requests.
   6  *
   7  * Copyright IBM Corporation 2009
   8  */
   9
  10 #ifndef ZFCP_REQLIST_H
  11 #define ZFCP_REQLIST_H
  12
  13 /* number of hash buckets */
  14 #define ZFCP_REQ_LIST_BUCKETS 128
  15
  16 /**
  17  * struct zfcp_reqlist - Container for request list (reqlist)
  18  * @lock: Spinlock for protecting the hash list
  19  * @list: Array of hashbuckets, each is a list of requests in this bucket
  20  */
  21 struct zfcp_reqlist {
  22         spinlock_t lock;
  23         struct list_head buckets[ZFCP_REQ_LIST_BUCKETS];
  24 };
  25
  26 static inline int zfcp_reqlist_hash(unsigned long req_id)
  27 {
  28         return req_id % ZFCP_REQ_LIST_BUCKETS;
  29 }
  30
  31 /**
  32  * zfcp_reqlist_alloc - Allocate and initialize reqlist
  33  *
  34  * Returns pointer to allocated reqlist on success, or NULL on
  35  * allocation failure.
  36  */
  37 static inline struct zfcp_reqlist *zfcp_reqlist_alloc(void)
  38 {
  39         unsigned int i;
  40         struct zfcp_reqlist *rl;
  41
  42         rl = kzalloc(sizeof(struct zfcp_reqlist), GFP_KERNEL);
  43         if (!rl)
  44                 return NULL;
  45
  46         spin_lock_init(&rl->lock);
  47
  48         for (i = 0; i < ZFCP_REQ_LIST_BUCKETS; i++)
  49                 INIT_LIST_HEAD(&rl->buckets[i]);
  50
  51         return rl;
  52 }
  53
  54 /**
  55  * zfcp_reqlist_isempty - Check whether the request list empty
  56  * @rl: pointer to reqlist
  57  *
  58  * Returns: 1 if list is empty, 0 if not
  59  */
  60 static inline int zfcp_reqlist_isempty(struct zfcp_reqlist *rl)
  61 {
  62         unsigned int i;
  63
  64         for (i = 0; i < ZFCP_REQ_LIST_BUCKETS; i++)
  65                 if (!list_empty(&rl->buckets[i]))
  66                         return 0;
  67         return 1;
  68 }
  69
  70 /**
  71  * zfcp_reqlist_free - Free allocated memory for reqlist
  72  * @rl: The reqlist where to free memory
  73  */
  74 static inline void zfcp_reqlist_free(struct zfcp_reqlist *rl)
  75 {
  76         /* sanity check */
  77         BUG_ON(!zfcp_reqlist_isempty(rl));
  78
  79         kfree(rl);
  80 }
  81
  82 static inline struct zfcp_fsf_req *
  83 _zfcp_reqlist_find(struct zfcp_reqlist *rl, unsigned long req_id)
  84 {
  85         struct zfcp_fsf_req *req;
  86         unsigned int i;
  87
  88         i = zfcp_reqlist_hash(req_id);
  89         list_for_each_entry(req, &rl->buckets[i], list)
  90                 if (req->req_id == req_id)
  91                         return req;
  92         return NULL;
  93 }
  94
  95 /**
  96  * zfcp_reqlist_find - Lookup FSF request by its request id
  97  * @rl: The reqlist where to lookup the FSF request
  98  * @req_id: The request id to look for
  99  *
 100  * Returns a pointer to the FSF request with the specified request id
 101  * or NULL if there is no known FSF request with this id.
 102  */
 103 static inline struct zfcp_fsf_req *
 104 zfcp_reqlist_find(struct zfcp_reqlist *rl, unsigned long req_id)
 105 {
 106         unsigned long flags;
 107         struct zfcp_fsf_req *req;
 108
 109         spin_lock_irqsave(&rl->lock, flags);
 110         req = _zfcp_reqlist_find(rl, req_id);
 111         spin_unlock_irqrestore(&rl->lock, flags);
 112
 113         return req;
 114 }
 115
 116 /**
 117  * zfcp_reqlist_find_rm - Lookup request by id and remove it from reqlist
 118  * @rl: reqlist where to search and remove entry
 119  * @req_id: The request id of the request to look for
 120  *
 121  * This functions tries to find the FSF request with the specified
 122  * id and then removes it from the reqlist. The reqlist lock is held
 123  * during both steps of the operation.
 124  *
 125  * Returns: Pointer to the FSF request if the request has been found,
 126  * NULL if it has not been found.
 127  */
 128 static inline struct zfcp_fsf_req *
 129 zfcp_reqlist_find_rm(struct zfcp_reqlist *rl, unsigned long req_id)
 130 {
 131         unsigned long flags;
 132         struct zfcp_fsf_req *req;
 133
 134         spin_lock_irqsave(&rl->lock, flags);
 135         req = _zfcp_reqlist_find(rl, req_id);
 136         if (req)
 137                 list_del(&req->list);
 138         spin_unlock_irqrestore(&rl->lock, flags);
 139
 140         return req;
 141 }
 142
 143 /**
 144  * zfcp_reqlist_add - Add entry to reqlist
 145  * @rl: reqlist where to add the entry
 146  * @req: The entry to add
 147  *
 148  * The request id always increases. As an optimization new requests
 149  * are added here with list_add_tail at the end of the bucket lists
 150  * while old requests are looked up starting at the beginning of the
 151  * lists.
 152  */
 153 static inline void zfcp_reqlist_add(struct zfcp_reqlist *rl,
 154                                     struct zfcp_fsf_req *req)
 155 {
 156         unsigned int i;
 157         unsigned long flags;
 158
 159         i = zfcp_reqlist_hash(req->req_id);
 160
 161         spin_lock_irqsave(&rl->lock, flags);
 162         list_add_tail(&req->list, &rl->buckets[i]);
 163         spin_unlock_irqrestore(&rl->lock, flags);
 164 }
 165
 166 /**
 167  * zfcp_reqlist_move - Move all entries from reqlist to simple list
 168  * @rl: The zfcp_reqlist where to remove all entries
 169  * @list: The list where to move all entries
 170  */
 171 static inline void zfcp_reqlist_move(struct zfcp_reqlist *rl,
 172                                      struct list_head *list)
 173 {
 174         unsigned int i;
 175         unsigned long flags;
 176
 177         spin_lock_irqsave(&rl->lock, flags);
 178         for (i = 0; i < ZFCP_REQ_LIST_BUCKETS; i++)
 179                 list_splice_init(&rl->buckets[i], list);
 180         spin_unlock_irqrestore(&rl->lock, flags);
 181 }
 182
 183 #endif /* ZFCP_REQLIST_H */