fs/reiser4/readahead.c

   1 /* Copyright 2001, 2002, 2003 by Hans Reiser, licensing governed by
   2  * reiser4/README */
   3
   4 #include "forward.h"
   5 #include "tree.h"
   6 #include "tree_walk.h"
   7 #include "super.h"
   8 #include "inode.h"
   9 #include "key.h"
  10 #include "znode.h"
  11
  12 #include <linux/swap.h>         /* for totalram_pages */
  13
  14 void reiser4_init_ra_info(ra_info_t *rai)
  15 {
  16         rai->key_to_stop = *reiser4_min_key();
  17 }
  18
  19 /* global formatted node readahead parameter. It can be set by mount option
  20  * -o readahead:NUM:1 */
  21 static inline int ra_adjacent_only(int flags)
  22 {
  23         return flags & RA_ADJACENT_ONLY;
  24 }
  25
  26 /* this is used by formatted_readahead to decide whether read for right neighbor
  27  * of node is to be issued. It returns 1 if right neighbor's first key is less
  28  * or equal to readahead's stop key */
  29 static int should_readahead_neighbor(znode * node, ra_info_t *info)
  30 {
  31         int result;
  32
  33         read_lock_dk(znode_get_tree(node));
  34         result = keyle(znode_get_rd_key(node), &info->key_to_stop);
  35         read_unlock_dk(znode_get_tree(node));
  36         return result;
  37 }
  38
  39 #define LOW_MEM_PERCENTAGE (5)
  40
  41 static int low_on_memory(void)
  42 {
  43         unsigned int freepages;
  44
  45         freepages = nr_free_pages();
  46         return freepages < (totalram_pages * LOW_MEM_PERCENTAGE / 100);
  47 }
  48
  49 /* start read for @node and for a few of its right neighbors */
  50 void formatted_readahead(znode * node, ra_info_t *info)
  51 {
  52         struct formatted_ra_params *ra_params;
  53         znode *cur;
  54         int i;
  55         int grn_flags;
  56         lock_handle next_lh;
  57
  58         /* do nothing if node block number has not been assigned to node (which
  59          * means it is still in cache). */
  60         if (reiser4_blocknr_is_fake(znode_get_block(node)))
  61                 return;
  62
  63         ra_params = get_current_super_ra_params();
  64
  65         if (znode_page(node) == NULL)
  66                 jstartio(ZJNODE(node));
  67
  68         if (znode_get_level(node) != LEAF_LEVEL)
  69                 return;
  70
  71         /* don't waste memory for read-ahead when low on memory */
  72         if (low_on_memory())
  73                 return;
  74
  75         /* We can have locked nodes on upper tree levels, in this situation lock
  76            priorities do not help to resolve deadlocks, we have to use TRY_LOCK
  77            here. */
  78         grn_flags = (GN_CAN_USE_UPPER_LEVELS | GN_TRY_LOCK);
  79
  80         i = 0;
  81         cur = zref(node);
  82         init_lh(&next_lh);
  83         while (i < ra_params->max) {
  84                 const reiser4_block_nr * nextblk;
  85
  86                 if (!should_readahead_neighbor(cur, info))
  87                         break;
  88
  89                 if (reiser4_get_right_neighbor
  90                     (&next_lh, cur, ZNODE_READ_LOCK, grn_flags))
  91                         break;
  92
  93                 nextblk = znode_get_block(next_lh.node);
  94                 if (reiser4_blocknr_is_fake(nextblk) ||
  95                     (ra_adjacent_only(ra_params->flags)
  96                      && *nextblk != *znode_get_block(cur) + 1))
  97                         break;
  98
  99                 zput(cur);
 100                 cur = zref(next_lh.node);
 101                 done_lh(&next_lh);
 102                 if (znode_page(cur) == NULL)
 103                         jstartio(ZJNODE(cur));
 104                 else
 105                         /* Do not scan read-ahead window if pages already
 106                          * allocated (and i/o already started). */
 107                         break;
 108
 109                 i++;
 110         }
 111         zput(cur);
 112         done_lh(&next_lh);
 113 }
 114
 115 void reiser4_readdir_readahead_init(struct inode *dir, tap_t *tap)
 116 {
 117         reiser4_key *stop_key;
 118
 119         assert("nikita-3542", dir != NULL);
 120         assert("nikita-3543", tap != NULL);
 121
 122         stop_key = &tap->ra_info.key_to_stop;
 123         /* initialize readdir readahead information: include into readahead
 124          * stat data of all files of the directory */
 125         set_key_locality(stop_key, get_inode_oid(dir));
 126         set_key_type(stop_key, KEY_SD_MINOR);
 127         set_key_ordering(stop_key, get_key_ordering(reiser4_max_key()));
 128         set_key_objectid(stop_key, get_key_objectid(reiser4_max_key()));
 129         set_key_offset(stop_key, get_key_offset(reiser4_max_key()));
 130 }
 131
 132 /*
 133    Local variables:
 134    c-indentation-style: "K&R"
 135    mode-name: "LC"
 136    c-basic-offset: 8
 137    tab-width: 8
 138    fill-column: 80
 139    End:
 140 */