Commit fb7d3bc4 authored by Jens Axboe's avatar Jens Axboe Committed by Andrew Morton
Browse files

mm/filemap: drop streaming/uncached pages when writeback completes 

If the folio is marked as streaming, drop pages when writeback completes. 
Intended to be used with RWF_DONTCACHE, to avoid needing sync writes for
uncached IO.

Link: https://lkml.kernel.org/r/20241220154831.1086649-10-axboe@kernel.dk


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Chris Mason <clm@meta.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8026e49b

mm/filemap.c

+28 −0
Original line number Diff line number Diff line
@@ -1571,6 +1571,27 @@ int folio_wait_private_2_killable(struct folio *folio) 
}

EXPORT_SYMBOL(folio_wait_private_2_killable);



/*

 * If folio was marked as dropbehind, then pages should be dropped when writeback

 * completes. Do that now. If we fail, it's likely because of a big folio -

 * just reset dropbehind for that case and latter completions should invalidate.

 */

static void folio_end_dropbehind_write(struct folio *folio)

{

	/*

	 * Hitting !in_task() should not happen off RWF_DONTCACHE writeback,

	 * but can happen if normal writeback just happens to find dirty folios

	 * that were created as part of uncached writeback, and that writeback

	 * would otherwise not need non-IRQ handling. Just skip the

	 * invalidation in that case.

	 */

	if (in_task() && folio_trylock(folio)) {

		if (folio->mapping)

			folio_unmap_invalidate(folio->mapping, folio, 0);

		folio_unlock(folio);

	}

}



/**

 * folio_end_writeback - End writeback against a folio.

 * @folio: The folio.
@@ -1581,6 +1602,8 @@ EXPORT_SYMBOL(folio_wait_private_2_killable); 
 */

void folio_end_writeback(struct folio *folio)

{

	bool folio_dropbehind = false;



	VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);



	/*
@@ -1602,9 +1625,14 @@ void folio_end_writeback(struct folio *folio) 
	 * reused before the folio_wake_bit().

	 */

	folio_get(folio);

	if (!folio_test_dirty(folio))

		folio_dropbehind = folio_test_clear_dropbehind(folio);

	if (__folio_end_writeback(folio))

		folio_wake_bit(folio, PG_writeback);

	acct_reclaim_writeback(folio);



	if (folio_dropbehind)

		folio_end_dropbehind_write(folio);

	folio_put(folio);

}

EXPORT_SYMBOL(folio_end_writeback);