fixlet: Remove fs_excl from struct task.

fs_excl is a poor man's priority inheritance for filesystems to hint to
the block layer that an operation is important. It was never clearly
specified, not widely adopted, and will not prevent starvation in many
cases (like across cgroups).

fs_excl was introduced with the time sliced CFQ IO scheduler, to
indicate when a process held FS exclusive resources and thus needed
a boost.

It doesn't cover all file systems, and it was never fully complete.
Lets kill it.

Signed-off-by: Justin TerAvest <teravest@google.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 762bd509b71b4008d3cc00d33bf78dc0a1917baf..d8b108737b7260fad72139fcf4e26960ebac41e9 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -134,7 +134,7 @@ struct cfq_queue {
 
        /* io prio of this group */
        unsigned short ioprio, org_ioprio;
-       unsigned short ioprio_class, org_ioprio_class;
+       unsigned short ioprio_class;
 
        pid_t pid;
 
@@ -2869,7 +2869,6 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
         * elevate the priority of this queue
         */
        cfqq->org_ioprio = cfqq->ioprio;
-       cfqq->org_ioprio_class = cfqq->ioprio_class;
        cfq_clear_cfqq_prio_changed(cfqq);
 }
 
@@ -3593,30 +3592,6 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
                cfq_schedule_dispatch(cfqd);
 }
 
-/*
- * we temporarily boost lower priority queues if they are holding fs exclusive
- * resources. they are boosted to normal prio (CLASS_BE/4)
- */
-static void cfq_prio_boost(struct cfq_queue *cfqq)
-{
-       if (has_fs_excl()) {
-               /*
-                * boost idle prio on transactions that would lock out other
-                * users of the filesystem
-                */
-               if (cfq_class_idle(cfqq))
-                       cfqq->ioprio_class = IOPRIO_CLASS_BE;
-               if (cfqq->ioprio > IOPRIO_NORM)
-                       cfqq->ioprio = IOPRIO_NORM;
-       } else {
-               /*
-                * unboost the queue (if needed)
-                */
-               cfqq->ioprio_class = cfqq->org_ioprio_class;
-               cfqq->ioprio = cfqq->org_ioprio;
-       }
-}
-
 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
 {
        if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
@@ -3647,7 +3622,6 @@ static int cfq_may_queue(struct request_queue *q, int rw)
        cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
        if (cfqq) {
                cfq_init_prio_data(cfqq, cic->ioc);
-               cfq_prio_boost(cfqq);
 
                return __cfq_may_queue(cfqq);
        }

diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index c5e82ece7c6c7d7afd2002d15c4293a99662bb4c..a159ba5a35e722457f83977bf4a82c1344528fc8 100644 (file)
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -678,23 +678,19 @@ struct buffer_chunk {
 static void write_chunk(struct buffer_chunk *chunk)
 {
        int i;
-       get_fs_excl();
        for (i = 0; i < chunk->nr; i++) {
                submit_logged_buffer(chunk->bh[i]);
        }
        chunk->nr = 0;
-       put_fs_excl();
 }
 
 static void write_ordered_chunk(struct buffer_chunk *chunk)
 {
        int i;
-       get_fs_excl();
        for (i = 0; i < chunk->nr; i++) {
                submit_ordered_buffer(chunk->bh[i]);
        }
        chunk->nr = 0;
-       put_fs_excl();
 }
 
 static int add_to_chunk(struct buffer_chunk *chunk, struct buffer_head *bh,
@@ -986,8 +982,6 @@ static int flush_commit_list(struct super_block *s,
                return 0;
        }
 
-       get_fs_excl();
-
        /* before we can put our commit blocks on disk, we have to make sure everyone older than
         ** us is on disk too
         */
@@ -1145,7 +1139,6 @@ static int flush_commit_list(struct super_block *s,
        if (retval)
                reiserfs_abort(s, retval, "Journal write error in %s",
                               __func__);
-       put_fs_excl();
        return retval;
 }
 
@@ -1374,8 +1367,6 @@ static int flush_journal_list(struct super_block *s,
                return 0;
        }
 
-       get_fs_excl();
-
        /* if all the work is already done, get out of here */
        if (atomic_read(&(jl->j_nonzerolen)) <= 0 &&
            atomic_read(&(jl->j_commit_left)) <= 0) {
@@ -1597,7 +1588,6 @@ static int flush_journal_list(struct super_block *s,
        put_journal_list(s, jl);
        if (flushall)
                mutex_unlock(&journal->j_flush_mutex);
-       put_fs_excl();
        return err;
 }
 
@@ -3108,7 +3098,6 @@ static int do_journal_begin_r(struct reiserfs_transaction_handle *th,
        th->t_trans_id = journal->j_trans_id;
        unlock_journal(sb);
        INIT_LIST_HEAD(&th->t_list);
-       get_fs_excl();
        return 0;
 
       out_fail:
@@ -3964,7 +3953,6 @@ static int do_journal_end(struct reiserfs_transaction_handle *th,
        flush = flags & FLUSH_ALL;
        wait_on_commit = flags & WAIT;
 
-       put_fs_excl();
        current->journal_info = th->t_handle_save;
        reiserfs_check_lock_depth(sb, "journal end");
        if (journal->j_len == 0) {
@@ -4316,4 +4304,3 @@ void reiserfs_abort_journal(struct super_block *sb, int errno)
        dump_stack();
 #endif
 }
-

diff --git a/fs/super.c b/fs/super.c
index ab3d672db0deae0a84a01bc1938cd967cc27e79f..cf12ba50973b8c5c73946f30f10cfbb9a3ee0a97 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -245,13 +245,11 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
  */
 void lock_super(struct super_block * sb)
 {
-       get_fs_excl();
        mutex_lock(&sb->s_lock);
 }
 
 void unlock_super(struct super_block * sb)
 {
-       put_fs_excl();
        mutex_unlock(&sb->s_lock);
 }
 
@@ -280,7 +278,6 @@ void generic_shutdown_super(struct super_block *sb)
        if (sb->s_root) {
                shrink_dcache_for_umount(sb);
                sync_filesystem(sb);
-               get_fs_excl();
                sb->s_flags &= ~MS_ACTIVE;
 
                fsnotify_unmount_inodes(&sb->s_inodes);
@@ -295,7 +292,6 @@ void generic_shutdown_super(struct super_block *sb)
                           "Self-destruct in 5 seconds.  Have a nice day...\n",
                           sb->s_id);
                }
-               put_fs_excl();
        }
        spin_lock(&sb_lock);
        /* should be initialized for __put_super_and_need_restart() */

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6e73e2e9ae33c5b7719f11fb303cee693dc1b043..f6c866c287b5e593bbe66dca3da5705ae6c89003 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1453,10 +1453,6 @@ enum {
 #define vfs_check_frozen(sb, level) \
        wait_event((sb)->s_wait_unfrozen, ((sb)->s_frozen < (level)))
 
-#define get_fs_excl() atomic_inc(&current->fs_excl)
-#define put_fs_excl() atomic_dec(&current->fs_excl)
-#define has_fs_excl() atomic_read(&current->fs_excl)
-
 /*
  * until VFS tracks user namespaces for inodes, just make all files
  * belong to init_user_ns

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 580f70c02391712f7cc0351d645361b683b82a8b..d14e058aaeedd6e63bafc24aadce24a78127d7a6 100644 (file)
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -176,7 +176,6 @@ extern struct cred init_cred;
        .alloc_lock     = __SPIN_LOCK_UNLOCKED(tsk.alloc_lock),         \
        .journal_info   = NULL,                                         \
        .cpu_timers     = INIT_CPU_TIMERS(tsk.cpu_timers),              \
-       .fs_excl        = ATOMIC_INIT(0),                               \
        .pi_lock        = __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock),        \
        .timer_slack_ns = 50000, /* 50 usec default slack */            \
        .pids = {                                                       \

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a837b20ba190330c23b59ec5a3fb584fc9f6308f..22f54249cde1929a5241fcb50a726ba99b2dd210 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1503,7 +1503,6 @@ struct task_struct {
        short il_next;
        short pref_node_fork;
 #endif
-       atomic_t fs_excl;       /* holding fs exclusive resources */
        struct rcu_head rcu;
 
        /*

diff --git a/kernel/exit.c b/kernel/exit.c
index f2b321bae44037c08d4b09b90b8610a80b979eb7..b412df45ea6cca4ae0d884306950ed9578573982 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -906,7 +906,6 @@ NORET_TYPE void do_exit(long code)
 
        profile_task_exit(tsk);
 
-       WARN_ON(atomic_read(&tsk->fs_excl));
        WARN_ON(blk_needs_flush_plug(tsk));
 
        if (unlikely(in_interrupt()))

diff --git a/kernel/fork.c b/kernel/fork.c
index 0276c30401a081132d1e4fadac663f3afdf292c0..30a0e86072230528467f9c652b72c90eb75c82d4 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -291,7 +291,6 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 
        /* One for us, one for whoever does the "release_task()" (usually parent) */
        atomic_set(&tsk->usage,2);
-       atomic_set(&tsk->fs_excl, 0);
 #ifdef CONFIG_BLK_DEV_IO_TRACE
        tsk->btrace_seq = 0;
 #endif