The patch titled
Subject: mm/filemap: drop streaming/uncached pages when writeback completes
has been added to the -mm mm-unstable branch. Its filename is
mm-filemap-drop-streaming-uncached-pages-when-writeback-completes.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-filemap-drop-streaming-uncached-pages-when-writeback-completes.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jens Axboe <axboe@xxxxxxxxx>
Subject: mm/filemap: drop streaming/uncached pages when writeback completes
Date: Fri, 20 Dec 2024 08:47:47 -0700
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@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Cc: Brian Foster <bfoster@xxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
--- a/mm/filemap.c~mm-filemap-drop-streaming-uncached-pages-when-writeback-completes
+++ a/mm/filemap.c
@@ -1571,6 +1571,27 @@ int folio_wait_private_2_killable(struct
}
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_killa
*/
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 *f
* 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);
_
Patches currently in -mm which might be from axboe@xxxxxxxxx are
mm-filemap-change-filemap_create_folio-to-take-a-struct-kiocb.patch
mm-filemap-use-page_cache_sync_ra-to-kick-off-read-ahead.patch
mm-readahead-add-folio-allocation-helper.patch
mm-add-pg_dropbehind-folio-flag.patch
mm-readahead-add-readahead_control-dropbehind-member.patch
mm-truncate-add-folio_unmap_invalidate-helper.patch
fs-add-rwf_dontcache-iocb-and-fop_dontcache-file_operations-flag.patch
mm-filemap-add-read-support-for-rwf_dontcache.patch
mm-filemap-drop-streaming-uncached-pages-when-writeback-completes.patch
mm-filemap-add-filemap_fdatawrite_range_kick-helper.patch
mm-call-filemap_fdatawrite_range_kick-after-iocb_dontcache-issue.patch
mm-add-fgp_dontcache-folio-creation-flag.patch
