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Subject[PATCH v9 32/61] mm: Convert page-writeback to XArray
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

Includes moving mapping_tagged() to fs.h as a static inline, and
changing it to return bool.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/fs.h | 17 +++++++++------
mm/page-writeback.c | 63 +++++++++++++++++++----------------------------------
2 files changed, 32 insertions(+), 48 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bb0731c05246..5daa26d04110 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -469,15 +469,18 @@ struct block_device {
struct mutex bd_fsfreeze_mutex;
} __randomize_layout;

+/* XArray tags, for tagging dirty and writeback pages in the pagecache. */
+#define PAGECACHE_TAG_DIRTY XA_TAG_0
+#define PAGECACHE_TAG_WRITEBACK XA_TAG_1
+#define PAGECACHE_TAG_TOWRITE XA_TAG_2
+
/*
- * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
- * radix trees
+ * Returns true if any of the pages in the mapping are marked with the tag.
*/
-#define PAGECACHE_TAG_DIRTY 0
-#define PAGECACHE_TAG_WRITEBACK 1
-#define PAGECACHE_TAG_TOWRITE 2
-
-int mapping_tagged(struct address_space *mapping, int tag);
+static inline bool mapping_tagged(struct address_space *mapping, xa_tag_t tag)
+{
+ return xa_tagged(&mapping->i_pages, tag);
+}

static inline void i_mmap_lock_write(struct address_space *mapping)
{
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5c1a3279e63f..195ccd0b30c8 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2098,34 +2098,25 @@ void __init page_writeback_init(void)
* dirty pages in the file (thus it is important for this function to be quick
* so that it can tag pages faster than a dirtying process can create them).
*/
-/*
- * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce the i_pages lock
- * latency.
- */
void tag_pages_for_writeback(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
-#define WRITEBACK_TAG_BATCH 4096
- unsigned long tagged = 0;
- struct radix_tree_iter iter;
- void **slot;
+ XA_STATE(xas, &mapping->i_pages, start);
+ unsigned int tagged = 0;
+ void *page;

- xa_lock_irq(&mapping->i_pages);
- radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start,
- PAGECACHE_TAG_DIRTY) {
- if (iter.index > end)
- break;
- radix_tree_iter_tag_set(&mapping->i_pages, &iter,
- PAGECACHE_TAG_TOWRITE);
- tagged++;
- if ((tagged % WRITEBACK_TAG_BATCH) != 0)
+ xas_lock_irq(&xas);
+ xas_for_each_tag(&xas, page, end, PAGECACHE_TAG_DIRTY) {
+ xas_set_tag(&xas, PAGECACHE_TAG_TOWRITE);
+ if (++tagged % XA_CHECK_SCHED)
continue;
- slot = radix_tree_iter_resume(slot, &iter);
- xa_unlock_irq(&mapping->i_pages);
+
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
cond_resched();
- xa_lock_irq(&mapping->i_pages);
+ xas_lock_irq(&xas);
}
- xa_unlock_irq(&mapping->i_pages);
+ xas_unlock_irq(&xas);
}
EXPORT_SYMBOL(tag_pages_for_writeback);

@@ -2165,7 +2156,7 @@ int write_cache_pages(struct address_space *mapping,
pgoff_t done_index;
int cycled;
int range_whole = 0;
- int tag;
+ xa_tag_t tag;

pagevec_init(&pvec);
if (wbc->range_cyclic) {
@@ -2446,7 +2437,7 @@ void account_page_cleaned(struct page *page, struct address_space *mapping,

/*
* For address_spaces which do not use buffers. Just tag the page as dirty in
- * its radix tree.
+ * the xarray.
*
* This is also used when a single buffer is being dirtied: we want to set the
* page dirty in that case, but not all the buffers. This is a "bottom-up"
@@ -2472,7 +2463,7 @@ int __set_page_dirty_nobuffers(struct page *page)
BUG_ON(page_mapping(page) != mapping);
WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
account_page_dirtied(page, mapping);
- radix_tree_tag_set(&mapping->i_pages, page_index(page),
+ __xa_set_tag(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_DIRTY);
xa_unlock_irqrestore(&mapping->i_pages, flags);
unlock_page_memcg(page);
@@ -2635,13 +2626,13 @@ EXPORT_SYMBOL(__cancel_dirty_page);
* Returns true if the page was previously dirty.
*
* This is for preparing to put the page under writeout. We leave the page
- * tagged as dirty in the radix tree so that a concurrent write-for-sync
+ * tagged as dirty in the xarray so that a concurrent write-for-sync
* can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
* implementation will run either set_page_writeback() or set_page_dirty(),
- * at which stage we bring the page's dirty flag and radix-tree dirty tag
+ * at which stage we bring the page's dirty flag and xarray dirty tag
* back into sync.
*
- * This incoherency between the page's dirty flag and radix-tree tag is
+ * This incoherency between the page's dirty flag and xarray tag is
* unfortunate, but it only exists while the page is locked.
*/
int clear_page_dirty_for_io(struct page *page)
@@ -2722,7 +2713,7 @@ int test_clear_page_writeback(struct page *page)
xa_lock_irqsave(&mapping->i_pages, flags);
ret = TestClearPageWriteback(page);
if (ret) {
- radix_tree_tag_clear(&mapping->i_pages, page_index(page),
+ __xa_clear_tag(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_WRITEBACK);
if (bdi_cap_account_writeback(bdi)) {
struct bdi_writeback *wb = inode_to_wb(inode);
@@ -2774,7 +2765,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
on_wblist = mapping_tagged(mapping,
PAGECACHE_TAG_WRITEBACK);

- radix_tree_tag_set(&mapping->i_pages, page_index(page),
+ __xa_set_tag(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_WRITEBACK);
if (bdi_cap_account_writeback(bdi))
inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
@@ -2788,10 +2779,10 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
sb_mark_inode_writeback(mapping->host);
}
if (!PageDirty(page))
- radix_tree_tag_clear(&mapping->i_pages, page_index(page),
+ __xa_clear_tag(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_DIRTY);
if (!keep_write)
- radix_tree_tag_clear(&mapping->i_pages, page_index(page),
+ __xa_clear_tag(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_TOWRITE);
xa_unlock_irqrestore(&mapping->i_pages, flags);
} else {
@@ -2807,16 +2798,6 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
}
EXPORT_SYMBOL(__test_set_page_writeback);

-/*
- * Return true if any of the pages in the mapping are marked with the
- * passed tag.
- */
-int mapping_tagged(struct address_space *mapping, int tag)
-{
- return radix_tree_tagged(&mapping->i_pages, tag);
-}
-EXPORT_SYMBOL(mapping_tagged);
-
/**
* wait_for_stable_page() - wait for writeback to finish, if necessary.
* @page: The page to wait on.
--
2.16.1
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