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Message-ID: <166924373637.1772793.2622483388224911574.stgit@warthog.procyon.org.uk>
Date: Wed, 23 Nov 2022 22:48:56 +0000
From: David Howells <dhowells@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matthew Wilcox <willy@...radead.org>,
Steve French <sfrench@...ba.org>,
Shyam Prasad N <nspmangalore@...il.com>,
Rohith Surabattula <rohiths.msft@...il.com>,
Dave Wysochanski <dwysocha@...hat.com>,
Dominique Martinet <asmadeus@...ewreck.org>,
Ilya Dryomov <idryomov@...il.com>, linux-cachefs@...hat.com,
linux-cifs@...r.kernel.org, linux-afs@...ts.infradead.org,
v9fs-developer@...ts.sourceforge.net, ceph-devel@...r.kernel.org,
linux-nfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, dhowells@...hat.com,
Matthew Wilcox <willy@...radead.org>,
Jeff Layton <jlayton@...nel.org>,
linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
v9fs-developer@...ts.sourceforge.net, linux-erofs@...ts.ozlabs.org,
linux-cachefs@...hat.com, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 3/3] mm: Make filemap_release_folio() better inform
shrink_folio_list()
Make filemap_release_folio() return one of three values:
(0) FILEMAP_CANT_RELEASE_FOLIO
Couldn't release the folio's private data, so the folio can't itself
be released.
(1) FILEMAP_RELEASED_FOLIO
The private data on the folio was released and the folio can be
released.
(2) FILEMAP_FOLIO_HAD_NO_PRIVATE
There was no private data on the folio and the folio can be released.
The first must be zero so that existing tests of !filemap_release_folio()
continue to work as expected; similarly the other two must both be non-zero
so that existing tests of filemap_release_folio() continue to work as
expected.
Using this, make shrink_folio_list() choose which of three cases to follow
based on the return from filemap_release_folio() rather than testing the
folio's private bit itself.
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Matthew Wilcox <willy@...radead.org>
cc: Linus Torvalds <torvalds@...ux-foundation.org>
cc: Steve French <sfrench@...ba.org>
cc: Shyam Prasad N <nspmangalore@...il.com>
cc: Rohith Surabattula <rohiths.msft@...il.com>
cc: Dave Wysochanski <dwysocha@...hat.com>
cc: Dominique Martinet <asmadeus@...ewreck.org>
cc: Ilya Dryomov <idryomov@...il.com>
cc: linux-cachefs@...hat.com
cc: linux-cifs@...r.kernel.org
cc: linux-afs@...ts.infradead.org
cc: v9fs-developer@...ts.sourceforge.net
cc: ceph-devel@...r.kernel.org
cc: linux-nfs@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-mm@...ck.org
Link: https://lore.kernel.org/r/1459152.1669208550@warthog.procyon.org.uk/ # v3
---
include/linux/pagemap.h | 7 ++++++-
mm/filemap.c | 20 ++++++++++++++------
mm/vmscan.c | 29 +++++++++++++++--------------
3 files changed, 35 insertions(+), 21 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 9a824b43c6af..b763182b6d3f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1124,7 +1124,12 @@ void replace_page_cache_page(struct page *old, struct page *new);
void delete_from_page_cache_batch(struct address_space *mapping,
struct folio_batch *fbatch);
int try_to_release_page(struct page *page, gfp_t gfp);
-bool filemap_release_folio(struct folio *folio, gfp_t gfp);
+enum filemap_released_folio {
+ FILEMAP_CANT_RELEASE_FOLIO = 0, /* (This must be 0) Release failed */
+ FILEMAP_RELEASED_FOLIO = 1, /* Folio's private data released */
+ FILEMAP_FOLIO_HAD_NO_PRIVATE = 2, /* Folio had no private data */
+};
+enum filemap_released_folio filemap_release_folio(struct folio *folio, gfp_t gfp);
loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
int whence);
diff --git a/mm/filemap.c b/mm/filemap.c
index 93757247cd11..859831c70439 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3934,20 +3934,28 @@ EXPORT_SYMBOL(generic_file_write_iter);
* this page (__GFP_IO), and whether the call may block
* (__GFP_RECLAIM & __GFP_FS).
*
- * Return: %true if the release was successful, otherwise %false.
+ * Return: %FILEMAP_RELEASED_FOLIO if the release was successful,
+ * %FILEMAP_CANT_RELEASE_FOLIO if the private data couldn't be released and
+ * %FILEMAP_FOLIO_HAD_NO_PRIVATE if there was no private data.
*/
-bool filemap_release_folio(struct folio *folio, gfp_t gfp)
+enum filemap_released_folio filemap_release_folio(struct folio *folio,
+ gfp_t gfp)
{
struct address_space * const mapping = folio->mapping;
+ bool released;
BUG_ON(!folio_test_locked(folio));
if (!folio_needs_release(folio))
- return true;
+ return FILEMAP_FOLIO_HAD_NO_PRIVATE;
if (folio_test_writeback(folio))
- return false;
+ return FILEMAP_CANT_RELEASE_FOLIO;
if (mapping && mapping->a_ops->release_folio)
- return mapping->a_ops->release_folio(folio, gfp);
- return try_to_free_buffers(folio);
+ released = mapping->a_ops->release_folio(folio, gfp);
+ else
+ released = try_to_free_buffers(folio);
+
+ return released ?
+ FILEMAP_RELEASED_FOLIO : FILEMAP_CANT_RELEASE_FOLIO;
}
EXPORT_SYMBOL(filemap_release_folio);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b9316f447238..d5c7b3be9947 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1978,25 +1978,26 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
* (refcount == 1) it can be freed. Otherwise, leave
* the folio on the LRU so it is swappable.
*/
- if (folio_needs_release(folio)) {
- if (!filemap_release_folio(folio, sc->gfp_mask))
- goto activate_locked;
+ switch (filemap_release_folio(folio, sc->gfp_mask)) {
+ case FILEMAP_CANT_RELEASE_FOLIO:
+ goto activate_locked;
+ case FILEMAP_RELEASED_FOLIO:
if (!mapping && folio_ref_count(folio) == 1) {
folio_unlock(folio);
if (folio_put_testzero(folio))
goto free_it;
- else {
- /*
- * rare race with speculative reference.
- * the speculative reference will free
- * this folio shortly, so we may
- * increment nr_reclaimed here (and
- * leave it off the LRU).
- */
- nr_reclaimed += nr_pages;
- continue;
- }
+ /*
+ * rare race with speculative reference. the
+ * speculative reference will free this folio
+ * shortly, so we may increment nr_reclaimed
+ * here (and leave it off the LRU).
+ */
+ nr_reclaimed += nr_pages;
+ continue;
}
+ break;
+ case FILEMAP_FOLIO_HAD_NO_PRIVATE:
+ break;
}
if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
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