fs/reiser4/ktxnmgrd.c

   1 /* Copyright 2002, 2003 by Hans Reiser, licensing governed by reiser4/README */
   2 /* Transaction manager daemon. */
   3
   4 /*
   5  * ktxnmgrd is a kernel daemon responsible for committing transactions. It is
   6  * needed/important for the following reasons:
   7  *
   8  *     1. in reiser4 atom is not committed immediately when last transaction
   9  *     handle closes, unless atom is either too old or too large (see
  10  *     atom_should_commit()). This is done to avoid committing too frequently.
  11  *     because:
  12  *
  13  *     2. sometimes we don't want to commit atom when closing last transaction
  14  *     handle even if it is old and fat enough. For example, because we are at
  15  *     this point under directory semaphore, and committing would stall all
  16  *     accesses to this directory.
  17  *
  18  * ktxnmgrd binds its time sleeping on condition variable. When is awakes
  19  * either due to (tunable) timeout or because it was explicitly woken up by
  20  * call to ktxnmgrd_kick(), it scans list of all atoms and commits ones
  21  * eligible.
  22  *
  23  */
  24
  25 #include "debug.h"
  26 #include "txnmgr.h"
  27 #include "tree.h"
  28 #include "ktxnmgrd.h"
  29 #include "super.h"
  30 #include "reiser4.h"
  31
  32 #include <linux/sched.h>        /* for struct task_struct */
  33 #include <linux/wait.h>
  34 #include <linux/suspend.h>
  35 #include <linux/kernel.h>
  36 #include <linux/writeback.h>
  37 #include <linux/kthread.h>
  38 #include <linux/freezer.h>
  39
  40 static int scan_mgr(struct super_block *);
  41
  42 /*
  43  * change current->comm so that ps, top, and friends will see changed
  44  * state. This serves no useful purpose whatsoever, but also costs nothing. May
  45  * be it will make lonely system administrator feeling less alone at 3 A.M.
  46  */
  47 #define set_comm(state)                                                 \
  48         snprintf(current->comm, sizeof(current->comm),                  \
  49                   "%s:%s:%s", __FUNCTION__, (super)->s_id, (state))
  50
  51 /**
  52  * ktxnmgrd - kernel txnmgr daemon
  53  * @arg: pointer to super block
  54  *
  55  * The background transaction manager daemon, started as a kernel thread during
  56  * reiser4 initialization.
  57  */
  58 static int ktxnmgrd(void *arg)
  59 {
  60         struct super_block *super;
  61         ktxnmgrd_context *ctx;
  62         txn_mgr *mgr;
  63         int done = 0;
  64
  65         super = arg;
  66         mgr = &get_super_private(super)->tmgr;
  67
  68         /*
  69          * do_fork() just copies task_struct into the new thread. ->fs_context
  70          * shouldn't be copied of course. This shouldn't be a problem for the
  71          * rest of the code though.
  72          */
  73         current->journal_info = NULL;
  74         ctx = mgr->daemon;
  75         while (1) {
  76                 try_to_freeze();
  77                 set_comm("wait");
  78                 {
  79                         DEFINE_WAIT(__wait);
  80
  81                         prepare_to_wait(&ctx->wait, &__wait,
  82                                         TASK_INTERRUPTIBLE);
  83                         if (kthread_should_stop())
  84                                 done = 1;
  85                         else
  86                                 schedule_timeout(ctx->timeout);
  87                         finish_wait(&ctx->wait, &__wait);
  88                 }
  89                 if (done)
  90                         break;
  91                 set_comm("run");
  92                 spin_lock(&ctx->guard);
  93                 /*
  94                  * wait timed out or ktxnmgrd was woken up by explicit request
  95                  * to commit something. Scan list of atoms in txnmgr and look
  96                  * for too old atoms.
  97                  */
  98                 do {
  99                         ctx->rescan = 0;
 100                         scan_mgr(super);
 101                         spin_lock(&ctx->guard);
 102                         if (ctx->rescan) {
 103                                 /*
 104                                  * the list could be modified while ctx
 105                                  * spinlock was released, we have to repeat
 106                                  * scanning from the beginning
 107                                  */
 108                                 break;
 109                         }
 110                 } while (ctx->rescan);
 111                 spin_unlock(&ctx->guard);
 112         }
 113         return 0;
 114 }
 115
 116 #undef set_comm
 117
 118 /**
 119  * reiser4_init_ktxnmgrd - initialize ktxnmgrd context and start kernel daemon
 120  * @super: pointer to super block
 121  *
 122  * Allocates and initializes ktxnmgrd_context, attaches it to transaction
 123  * manager. Starts kernel txnmgr daemon. This is called on mount.
 124  */
 125 int reiser4_init_ktxnmgrd(struct super_block *super)
 126 {
 127         txn_mgr *mgr;
 128         ktxnmgrd_context *ctx;
 129
 130         mgr = &get_super_private(super)->tmgr;
 131
 132         assert("zam-1014", mgr->daemon == NULL);
 133
 134         ctx = kzalloc(sizeof(ktxnmgrd_context), reiser4_ctx_gfp_mask_get());
 135         if (!ctx)
 136                 return RETERR(-ENOMEM);
 137
 138         assert("nikita-2442", ctx != NULL);
 139
 140         init_waitqueue_head(&ctx->wait);
 141
 142         /*kcond_init(&ctx->startup);*/
 143         spin_lock_init(&ctx->guard);
 144         ctx->timeout = REISER4_TXNMGR_TIMEOUT;
 145         ctx->rescan = 1;
 146         mgr->daemon = ctx;
 147
 148         ctx->tsk = kthread_run(ktxnmgrd, super, "ktxnmgrd");
 149         if (IS_ERR(ctx->tsk)) {
 150                 int ret = PTR_ERR(ctx->tsk);
 151                 mgr->daemon = NULL;
 152                 kfree(ctx);
 153                 return RETERR(ret);
 154         }
 155         return 0;
 156 }
 157
 158 void ktxnmgrd_kick(txn_mgr *mgr)
 159 {
 160         assert("nikita-3234", mgr != NULL);
 161         assert("nikita-3235", mgr->daemon != NULL);
 162         wake_up(&mgr->daemon->wait);
 163 }
 164
 165 int is_current_ktxnmgrd(void)
 166 {
 167         return (get_current_super_private()->tmgr.daemon->tsk == current);
 168 }
 169
 170 /**
 171  * scan_mgr - commit atoms which are to be committed
 172  * @super: super block to commit atoms of
 173  *
 174  * Commits old atoms.
 175  */
 176 static int scan_mgr(struct super_block *super)
 177 {
 178         int ret;
 179         reiser4_context ctx;
 180
 181         init_stack_context(&ctx, super);
 182
 183         ret = commit_some_atoms(&get_super_private(super)->tmgr);
 184
 185         reiser4_exit_context(&ctx);
 186         return ret;
 187 }
 188
 189 /**
 190  * reiser4_done_ktxnmgrd - stop kernel thread and frees ktxnmgrd context
 191  * @mgr:
 192  *
 193  * This is called on umount. Stops ktxnmgrd and free t
 194  */
 195 void reiser4_done_ktxnmgrd(struct super_block *super)
 196 {
 197         txn_mgr *mgr;
 198
 199         mgr = &get_super_private(super)->tmgr;
 200         assert("zam-1012", mgr->daemon != NULL);
 201
 202         kthread_stop(mgr->daemon->tsk);
 203         kfree(mgr->daemon);
 204         mgr->daemon = NULL;
 205 }
 206
 207 /*
 208  * Local variables:
 209  * c-indentation-style: "K&R"
 210  * mode-name: "LC"
 211  * c-basic-offset: 8
 212  * tab-width: 8
 213  * fill-column: 120
 214  * End:
 215  */