[PATCH 07/19] writeback: Factor writeback_get_batch() out of write_cache_pages()

Christoph Hellwig
2024-01-25T08:58:38Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

This simple helper will be the basis of the writeback iterator.
To make this work, we need to remember the current index
and end positions in writeback_control.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
[hch: heavily rebased, add helpers to get the tag and end index,
don't keep the end index in struct writeback_control]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
---
include/linux/writeback.h | 1 +
mm/page-writeback.c | 49 +++++++++++++++++++++++++--------------
2 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 7d60a68fa4ea47..a091817a5dba55 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -81,6 +81,7 @@ struct writeback_control {

/* internal fields used by the ->writepages implementation: */
struct folio_batch fbatch;
+ pgoff_t index;
int err;

#ifdef CONFIG_CGROUP_WRITEBACK
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index fcd90a176d806c..426d929741e46e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2383,6 +2383,29 @@ static void writeback_finish(struct address_space *mapping,
}
}

+static xa_mark_t wbc_to_tag(struct writeback_control *wbc)
+{
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+ return PAGECACHE_TAG_TOWRITE;
+ return PAGECACHE_TAG_DIRTY;
+}
+
+static pgoff_t wbc_end(struct writeback_control *wbc)
+{
+ if (wbc->range_cyclic)
+ return -1;
+ return wbc->range_end >> PAGE_SHIFT;
+}
+
+static void writeback_get_batch(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ folio_batch_release(&wbc->fbatch);
+ cond_resched();
+ filemap_get_folios_tag(mapping, &wbc->index, wbc_end(wbc),
+ wbc_to_tag(wbc), &wbc->fbatch);
+}
+
/**
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
* @mapping: address space structure to write
@@ -2419,38 +2442,30 @@ int write_cache_pages(struct address_space *mapping,
void *data)
{
int error;
- int nr_folios;
- pgoff_t index;
pgoff_t end; /* Inclusive */
- xa_mark_t tag;

if (wbc->range_cyclic) {
- index = mapping->writeback_index; /* prev offset */
+ wbc->index = mapping->writeback_index; /* prev offset */
end = -1;
} else {
- index = wbc->range_start >> PAGE_SHIFT;
+ wbc->index = wbc->range_start >> PAGE_SHIFT;
end = wbc->range_end >> PAGE_SHIFT;
}
- if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
- tag_pages_for_writeback(mapping, index, end);
- tag = PAGECACHE_TAG_TOWRITE;
- } else {
- tag = PAGECACHE_TAG_DIRTY;
- }
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+ tag_pages_for_writeback(mapping, wbc->index, end);

folio_batch_init(&wbc->fbatch);
wbc->err = 0;

- while (index <= end) {
+ while (wbc->index <= end) {
int i;

- nr_folios = filemap_get_folios_tag(mapping, &index, end,
- tag, &wbc->fbatch);
+ writeback_get_batch(mapping, wbc);

- if (nr_folios == 0)
+ if (wbc->fbatch.nr == 0)
break;

- for (i = 0; i < nr_folios; i++) {
+ for (i = 0; i < wbc->fbatch.nr; i++) {
struct folio *folio = wbc->fbatch.folios[i];
unsigned long nr;

@@ -2525,8 +2540,6 @@ int write_cache_pages(struct address_space *mapping,
return error;
}
}
- folio_batch_release(&wbc->fbatch);
- cond_resched();
}

writeback_finish(mapping, wbc, 0);
--
2.39.2