block: remove per-queue plugging

Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 6 insertions, 61 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 83a45d35468b..380776c2a9ac 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -155,45 +155,15 @@ void remove_from_page_cache(struct page *page)
 }
 EXPORT_SYMBOL(remove_from_page_cache);
 
-static int sync_page(void *word)
+static int sleep_on_page(void *word)
 {
-        struct address_space *mapping;
-        struct page *page;
-
-        page = container_of((unsigned long *)word, struct page, flags);
-
-        /*
-         * page_mapping() is being called without PG_locked held.
-         * Some knowledge of the state and use of the page is used to
-         * reduce the requirements down to a memory barrier.
-         * The danger here is of a stale page_mapping() return value
-         * indicating a struct address_space different from the one it's
-         * associated with when it is associated with one.
-         * After smp_mb(), it's either the correct page_mapping() for
-         * the page, or an old page_mapping() and the page's own
-         * page_mapping() has gone NULL.
-         * The ->sync_page() address_space operation must tolerate
-         * page_mapping() going NULL. By an amazing coincidence,
-         * this comes about because none of the users of the page
-         * in the ->sync_page() methods make essential use of the
-         * page_mapping(), merely passing the page down to the backing
-         * device's unplug functions when it's non-NULL, which in turn
-         * ignore it for all cases but swap, where only page_private(page) is
-         * of interest. When page_mapping() does go NULL, the entire
-         * call stack gracefully ignores the page and returns.
-         * -- wli
-         */
-        smp_mb();
-        mapping = page_mapping(page);
-        if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
-                mapping->a_ops->sync_page(page);
         io_schedule();
         return 0;
 }
 
-static int sync_page_killable(void *word)
+static int sleep_on_page_killable(void *word)
 {
-        sync_page(word);
+        sleep_on_page(word);
         return fatal_signal_pending(current) ? -EINTR : 0;
 }
 
@@ -479,12 +449,6 @@ struct page *__page_cache_alloc(gfp_t gfp)
 EXPORT_SYMBOL(__page_cache_alloc);
 #endif
 
-static int __sleep_on_page_lock(void *word)
-{
-        io_schedule();
-        return 0;
-}
-
 /*
  * In order to wait for pages to become available there must be
  * waitqueues associated with pages. By using a hash table of
@@ -512,7 +476,7 @@ void wait_on_page_bit(struct page *page, int bit_nr)
         DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 
         if (test_bit(bit_nr, &page->flags))
-                __wait_on_bit(page_waitqueue(page), &wait, sync_page,
+                __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
                                                         TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL(wait_on_page_bit);
@@ -576,17 +540,12 @@ EXPORT_SYMBOL(end_page_writeback);
 /**
  * __lock_page - get a lock on the page, assuming we need to sleep to get it
  * @page: the page to lock
- *
- * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
- * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
- * chances are that on the second loop, the block layer's plug list is empty,
- * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
  */
 void __lock_page(struct page *page)
 {
         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 
-        __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
+        __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
                                                         TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL(__lock_page);
@@ -596,24 +555,10 @@ int __lock_page_killable(struct page *page)
         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 
         return __wait_on_bit_lock(page_waitqueue(page), &wait,
-                                        sync_page_killable, TASK_KILLABLE);
+                                        sleep_on_page_killable, TASK_KILLABLE);
 }
 EXPORT_SYMBOL_GPL(__lock_page_killable);
 
-/**
- * __lock_page_nosync - get a lock on the page, without calling sync_page()
- * @page: the page to lock
- *
- * Variant of lock_page that does not require the caller to hold a reference
- * on the page's mapping.
- */
-void __lock_page_nosync(struct page *page)
-{
-        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
-        __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
-                                                        TASK_UNINTERRUPTIBLE);
-}
-
 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
                          unsigned int flags)
 {