[PATCH v13 067/137] mm/writeback: Add folio_start_writeback()

Matthew Wilcox (Oracle)
2021-07-12T03:44:03Z

Rename set_page_writeback() to folio_start_writeback() to match
folio_end_writeback(). Do not bother with wrappers that return void;
callers are perfectly capable of ignoring return values.

Add wrappers for set_page_writeback(), set_page_writeback_keepwrite() and
test_set_page_writeback() for compatibililty with existing filesystems.
The main advantage of this patch is getting the statistics right,
although it does eliminate a couple of calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
include/linux/page-flags.h | 19 +++++++++---------
mm/folio-compat.c | 6 ++++++
mm/page-writeback.c | 40 ++++++++++++++++++++------------------
3 files changed, 37 insertions(+), 28 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index fb5219ab9eee..3ac85230bec8 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -655,21 +655,22 @@ static __always_inline void SetPageUptodate(struct page *page)

CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)

-int __test_set_page_writeback(struct page *page, bool keep_write);
+bool __folio_start_writeback(struct folio *folio, bool keep_write);
+bool set_page_writeback(struct page *page);

-#define test_set_page_writeback(page) \
- __test_set_page_writeback(page, false)
-#define test_set_page_writeback_keepwrite(page) \
- __test_set_page_writeback(page, true)
+#define folio_start_writeback(folio) \
+ __folio_start_writeback(folio, false)
+#define folio_start_writeback_keepwrite(folio) \
+ __folio_start_writeback(folio, true)

-static inline void set_page_writeback(struct page *page)
+static inline void set_page_writeback_keepwrite(struct page *page)
{
- test_set_page_writeback(page);
+ folio_start_writeback_keepwrite(page_folio(page));
}

-static inline void set_page_writeback_keepwrite(struct page *page)
+static inline bool test_set_page_writeback(struct page *page)
{
- test_set_page_writeback_keepwrite(page);
+ return set_page_writeback(page);
}

__PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 2ccd8f213fc4..10ce5582d869 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -71,3 +71,9 @@ void migrate_page_copy(struct page *newpage, struct page *page)
}
EXPORT_SYMBOL(migrate_page_copy);
#endif
+
+bool set_page_writeback(struct page *page)
+{
+ return folio_start_writeback(page_folio(page));
+}
+EXPORT_SYMBOL(set_page_writeback);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c173fc831d3a..2b908c1913ca 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2773,21 +2773,23 @@ bool __folio_end_writeback(struct folio *folio)
return ret;
}

-int __test_set_page_writeback(struct page *page, bool keep_write)
+bool __folio_start_writeback(struct folio *folio, bool keep_write)
{
- struct address_space *mapping = page_mapping(page);
- int ret, access_ret;
+ long nr = folio_nr_pages(folio);
+ struct address_space *mapping = folio_mapping(folio);
+ bool ret;
+ int access_ret;

- lock_page_memcg(page);
+ folio_memcg_lock(folio);
if (mapping && mapping_use_writeback_tags(mapping)) {
- XA_STATE(xas, &mapping->i_pages, page_index(page));
+ XA_STATE(xas, &mapping->i_pages, folio_index(folio));
struct inode *inode = mapping->host;
struct backing_dev_info *bdi = inode_to_bdi(inode);
unsigned long flags;

xas_lock_irqsave(&xas, flags);
xas_load(&xas);
- ret = TestSetPageWriteback(page);
+ ret = folio_test_set_writeback_flag(folio);
if (!ret) {
bool on_wblist;

@@ -2796,40 +2798,40 @@ int __test_set_page_writeback(struct page *page, bool keep_write)

xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT)
- inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
+ wb_stat_mod(inode_to_wb(inode), WB_WRITEBACK,
+ nr);

/*
- * We can come through here when swapping anonymous
- * pages, so we don't necessarily have an inode to track
- * for sync.
+ * We can come through here when swapping
+ * anonymous folios, so we don't necessarily
+ * have an inode to track for sync.
*/
if (mapping->host && !on_wblist)
sb_mark_inode_writeback(mapping->host);
}
- if (!PageDirty(page))
+ if (!folio_dirty(folio))
xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
if (!keep_write)
xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
xas_unlock_irqrestore(&xas, flags);
} else {
- ret = TestSetPageWriteback(page);
+ ret = folio_test_set_writeback_flag(folio);
}
if (!ret) {
- inc_lruvec_page_state(page, NR_WRITEBACK);
- inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
+ lruvec_stat_mod_folio(folio, NR_WRITEBACK, nr);
+ zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr);
}
- unlock_page_memcg(page);
- access_ret = arch_make_page_accessible(page);
+ folio_memcg_unlock(folio);
+ access_ret = arch_make_folio_accessible(folio);
/*
* If writeback has been triggered on a page that cannot be made
* accessible, it is too late to recover here.
*/
- VM_BUG_ON_PAGE(access_ret != 0, page);
+ VM_BUG_ON_FOLIO(access_ret != 0, folio);

return ret;
-
}
-EXPORT_SYMBOL(__test_set_page_writeback);
+EXPORT_SYMBOL(__folio_start_writeback);

/**
* folio_wait_writeback - Wait for a folio to finish writeback.
--
2.30.2