Commit 751e0d55 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

writeback: factor writeback_get_batch() out of write_cache_pages() 

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.

[hch@lst.de: heavily rebased, add helpers to get the tag and end index, don't keep the end index in struct writeback_control]
Link: https://lkml.kernel.org/r/20240215063649.2164017-9-hch@lst.de


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarDave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b1793929

include/linux/writeback.h

+6 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/flex_proportions.h>

#include <linux/backing-dev-defs.h>

#include <linux/blk_types.h>

#include <linux/pagevec.h>



struct bio;
@@ -40,6 +41,7 @@ enum writeback_sync_modes { 
 * in a manner such that unspecified fields are set to zero.

 */

struct writeback_control {

	/* public fields that can be set and/or consumed by the caller: */

	long nr_to_write;		/* Write this many pages, and decrement

					   this for each page written */

	long pages_skipped;		/* Pages which were not written */
@@ -77,6 +79,10 @@ struct writeback_control { 
	 */

	struct swap_iocb **swap_plug;



	/* internal fields used by the ->writepages implementation: */

	struct folio_batch fbatch;

	pgoff_t index;



#ifdef CONFIG_CGROUP_WRITEBACK

	struct bdi_writeback *wb;	/* wb this writeback is issued under */

	struct inode *inode;		/* inode being written out */

mm/page-writeback.c

+38 −22
Original line number Diff line number Diff line
@@ -2392,6 +2392,29 @@ static bool folio_prepare_writeback(struct address_space *mapping, 
	return true;

}



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
@@ -2429,38 +2452,32 @@ int write_cache_pages(struct address_space *mapping, 
{

	int ret = 0;

	int error;

	struct folio_batch fbatch;

	struct folio *folio;

	int nr_folios;

	pgoff_t index;

	pgoff_t end;		/* Inclusive */

	xa_mark_t tag;



	folio_batch_init(&fbatch);

	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;

	}

	while (index <= end) {

	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)

		tag_pages_for_writeback(mapping, wbc->index, end);



	folio_batch_init(&wbc->fbatch);



	while (wbc->index <= end) {

		int i;



		nr_folios = filemap_get_folios_tag(mapping, &index, end,

				tag, &fbatch);

		writeback_get_batch(mapping, wbc);



		if (nr_folios == 0)

		if (wbc->fbatch.nr == 0)

			break;



		for (i = 0; i < nr_folios; i++) {

			folio = fbatch.folios[i];

		for (i = 0; i < wbc->fbatch.nr; i++) {

			folio = wbc->fbatch.folios[i];



			folio_lock(folio);

			if (!folio_prepare_writeback(mapping, wbc, folio)) {

				folio_unlock(folio);
@@ -2498,8 +2515,6 @@ int write_cache_pages(struct address_space *mapping, 
					goto done;

			}

		}

		folio_batch_release(&fbatch);

		cond_resched();

	}



	/*
@@ -2512,6 +2527,7 @@ int write_cache_pages(struct address_space *mapping, 
	 * of the file if we are called again, which can only happen due to

	 * -ENOMEM from the file system.

	 */

	folio_batch_release(&wbc->fbatch);

	if (wbc->range_cyclic)

		mapping->writeback_index = 0;

	return ret;
@@ -2519,7 +2535,7 @@ int write_cache_pages(struct address_space *mapping, 
done:

	if (wbc->range_cyclic)

		mapping->writeback_index = folio->index + folio_nr_pages(folio);

	folio_batch_release(&fbatch);

	folio_batch_release(&wbc->fbatch);

	return error;

}

EXPORT_SYMBOL(write_cache_pages);