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mm/filemap: Add folio_wait_bit() 

Rename wait_on_page_bit() to folio_wait_bit().  We must always wait on
the folio, otherwise we won't be woken up due to the tail page hashing
to a different bucket from the head page.

This commit shrinks the kernel by 770 bytes, mostly due to moving
the page waitqueue lookup into folio_wait_bit_common().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-03-04 12:02:54 -05:00
parent a49d0c5077
commit 101c0bf67f
3 changed files with 43 additions and 48 deletions
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10
include/linux/pagemap.h
View File

@ -728,11 +728,11 @@ static inline bool lock_page_or_retry(struct page *page, struct mm_struct *mm,
}
/*
* This is exported only for wait_on_page_locked/wait_on_page_writeback, etc.,
* This is exported only for folio_wait_locked/folio_wait_writeback, etc.,
* and should not be used directly.
*/
extern void wait_on_page_bit(struct page *page, int bit_nr);
extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
void folio_wait_bit(struct folio *folio, int bit_nr);
int folio_wait_bit_killable(struct folio *folio, int bit_nr);
/*
* Wait for a folio to be unlocked.
@ -744,14 +744,14 @@ extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
static inline void folio_wait_locked(struct folio *folio)
{
if (folio_test_locked(folio))
wait_on_page_bit(&folio->page, PG_locked);
folio_wait_bit(folio, PG_locked);
}
static inline int folio_wait_locked_killable(struct folio *folio)
{
if (!folio_test_locked(folio))
return 0;
return wait_on_page_bit_killable(&folio->page, PG_locked);
return folio_wait_bit_killable(folio, PG_locked);
}
static inline void wait_on_page_locked(struct page *page)

77
mm/filemap.c
View File

@ -1157,7 +1157,7 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync,
*
* So update the flags atomically, and wake up the waiter
* afterwards to avoid any races. This store-release pairs
* with the load-acquire in wait_on_page_bit_common().
* with the load-acquire in folio_wait_bit_common().
*/
smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
wake_up_state(wait->private, mode);
@ -1238,7 +1238,7 @@ static void folio_wake(struct folio *folio, int bit)
}
/*
* A choice of three behaviors for wait_on_page_bit_common():
* A choice of three behaviors for folio_wait_bit_common():
*/
enum behavior {
EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
@ -1253,16 +1253,16 @@ enum behavior {
};
/*
* Attempt to check (or get) the page bit, and mark us done
* Attempt to check (or get) the folio flag, and mark us done
* if successful.
*/
static inline bool trylock_page_bit_common(struct page *page, int bit_nr,
static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
struct wait_queue_entry *wait)
{
if (wait->flags & WQ_FLAG_EXCLUSIVE) {
if (test_and_set_bit(bit_nr, &page->flags))
if (test_and_set_bit(bit_nr, &folio->flags))
return false;
} else if (test_bit(bit_nr, &page->flags))
} else if (test_bit(bit_nr, &folio->flags))
return false;
wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
@ -1272,9 +1272,10 @@ static inline bool trylock_page_bit_common(struct page *page, int bit_nr,
/* How many times do we accept lock stealing from under a waiter? */
int sysctl_page_lock_unfairness = 5;
static inline int wait_on_page_bit_common(wait_queue_head_t *q,
struct page *page, int bit_nr, int state, enum behavior behavior)
static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
int state, enum behavior behavior)
{
wait_queue_head_t *q = page_waitqueue(&folio->page);
int unfairness = sysctl_page_lock_unfairness;
struct wait_page_queue wait_page;
wait_queue_entry_t *wait = &wait_page.wait;
@ -1283,8 +1284,8 @@ static inline int wait_on_page_bit_common(wait_queue_head_t *q,
unsigned long pflags;
if (bit_nr == PG_locked &&
!PageUptodate(page) && PageWorkingset(page)) {
if (!PageSwapBacked(page)) {
!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
if (!folio_test_swapbacked(folio)) {
delayacct_thrashing_start();
delayacct = true;
}
@ -1294,7 +1295,7 @@ static inline int wait_on_page_bit_common(wait_queue_head_t *q,
init_wait(wait);
wait->func = wake_page_function;
wait_page.page = page;
wait_page.page = &folio->page;
wait_page.bit_nr = bit_nr;
repeat:
@ -1309,7 +1310,7 @@ repeat:
* Do one last check whether we can get the
* page bit synchronously.
*
* Do the SetPageWaiters() marking before that
* Do the folio_set_waiters() marking before that
* to let any waker we _just_ missed know they
* need to wake us up (otherwise they'll never
* even go to the slow case that looks at the
@ -1320,8 +1321,8 @@ repeat:
* lock to avoid races.
*/
spin_lock_irq(&q->lock);
SetPageWaiters(page);
if (!trylock_page_bit_common(page, bit_nr, wait))
folio_set_waiters(folio);
if (!folio_trylock_flag(folio, bit_nr, wait))
__add_wait_queue_entry_tail(q, wait);
spin_unlock_irq(&q->lock);
@ -1331,10 +1332,10 @@ repeat:
* see whether the page bit testing has already
* been done by the wake function.
*
* We can drop our reference to the page.
* We can drop our reference to the folio.
*/
if (behavior == DROP)
put_page(page);
folio_put(folio);
/*
* Note that until the "finish_wait()", or until
@ -1371,7 +1372,7 @@ repeat:
*
* And if that fails, we'll have to retry this all.
*/
if (unlikely(test_and_set_bit(bit_nr, &page->flags)))
if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
goto repeat;
wait->flags |= WQ_FLAG_DONE;
@ -1380,7 +1381,7 @@ repeat:
/*
* If a signal happened, this 'finish_wait()' may remove the last
* waiter from the wait-queues, but the PageWaiters bit will remain
* waiter from the wait-queues, but the folio waiters bit will remain
* set. That's ok. The next wakeup will take care of it, and trying
* to do it here would be difficult and prone to races.
*/
@ -1411,19 +1412,17 @@ repeat:
return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
}
void wait_on_page_bit(struct page *page, int bit_nr)
void folio_wait_bit(struct folio *folio, int bit_nr)
{
wait_queue_head_t *q = page_waitqueue(page);
wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
}
EXPORT_SYMBOL(wait_on_page_bit);
EXPORT_SYMBOL(folio_wait_bit);
int wait_on_page_bit_killable(struct page *page, int bit_nr)
int folio_wait_bit_killable(struct folio *folio, int bit_nr)
{
wait_queue_head_t *q = page_waitqueue(page);
return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED);
return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
}
EXPORT_SYMBOL(wait_on_page_bit_killable);
EXPORT_SYMBOL(folio_wait_bit_killable);
/**
* put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
@ -1440,11 +1439,8 @@ EXPORT_SYMBOL(wait_on_page_bit_killable);
*/
int put_and_wait_on_page_locked(struct page *page, int state)
{
wait_queue_head_t *q;
page = compound_head(page);
q = page_waitqueue(page);
return wait_on_page_bit_common(q, page, PG_locked, state, DROP);
return folio_wait_bit_common(page_folio(page), PG_locked, state,
DROP);
}
/**
@ -1538,9 +1534,10 @@ EXPORT_SYMBOL(end_page_private_2);
*/
void wait_on_page_private_2(struct page *page)
{
page = compound_head(page);
while (PagePrivate2(page))
wait_on_page_bit(page, PG_private_2);
struct folio *folio = page_folio(page);
while (folio_test_private_2(folio))
folio_wait_bit(folio, PG_private_2);
}
EXPORT_SYMBOL(wait_on_page_private_2);
@ -1557,11 +1554,11 @@ EXPORT_SYMBOL(wait_on_page_private_2);
*/
int wait_on_page_private_2_killable(struct page *page)
{
struct folio *folio = page_folio(page);
int ret = 0;
page = compound_head(page);
while (PagePrivate2(page)) {
ret = wait_on_page_bit_killable(page, PG_private_2);
while (folio_test_private_2(folio)) {
ret = folio_wait_bit_killable(folio, PG_private_2);
if (ret < 0)
break;
}
@ -1638,16 +1635,14 @@ EXPORT_SYMBOL_GPL(page_endio);
*/
void __folio_lock(struct folio *folio)
{
wait_queue_head_t *q = page_waitqueue(&folio->page);
wait_on_page_bit_common(q, &folio->page, PG_locked, TASK_UNINTERRUPTIBLE,
folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
EXCLUSIVE);
}
EXPORT_SYMBOL(__folio_lock);
int __folio_lock_killable(struct folio *folio)
{
wait_queue_head_t *q = page_waitqueue(&folio->page);
return wait_on_page_bit_common(q, &folio->page, PG_locked, TASK_KILLABLE,
return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
EXCLUSIVE);
}
EXPORT_SYMBOL_GPL(__folio_lock_killable);

4
mm/page-writeback.c
View File

@ -2889,7 +2889,7 @@ void folio_wait_writeback(struct folio *folio)
{
while (folio_test_writeback(folio)) {
trace_wait_on_page_writeback(&folio->page, folio_mapping(folio));
wait_on_page_bit(&folio->page, PG_writeback);
folio_wait_bit(folio, PG_writeback);
}
}
EXPORT_SYMBOL_GPL(folio_wait_writeback);
@ -2911,7 +2911,7 @@ int folio_wait_writeback_killable(struct folio *folio)
{
while (folio_test_writeback(folio)) {
trace_wait_on_page_writeback(&folio->page, folio_mapping(folio));
if (wait_on_page_bit_killable(&folio->page, PG_writeback))
if (folio_wait_bit_killable(folio, PG_writeback))
return -EINTR;
}