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	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: Jens 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: Andrew Morton <akpm@linux-foundation.org>
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							|  | @ -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); | ||||
|  |  | |||
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	 Jens Axboe
						Jens Axboe