+ pagevec-add-ability-to-iterate-a-queue.patch added to mm-unstable branch

+ pagevec-add-ability-to-iterate-a-queue.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: pagevec: add ability to iterate a queue
has been added to the -mm mm-unstable branch.  Its filename is
     pagevec-add-ability-to-iterate-a-queue.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/pagevec-add-ability-to-iterate-a-queue.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: pagevec: add ability to iterate a queue
Date: Thu, 15 Feb 2024 07:36:45 +0100

Add a loop counter inside the folio_batch to let us iterate from 0-nr
instead of decrementing nr and treating the batch as a stack.  It would
generate some very weird and suboptimal I/O patterns for page writeback to
iterate over the batch as a stack.

Link: https://lkml.kernel.org/r/20240215063649.2164017-11-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/pagevec.h |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

--- a/include/linux/pagevec.h~pagevec-add-ability-to-iterate-a-queue
+++ a/include/linux/pagevec.h
@@ -27,6 +27,7 @@ struct folio;
  */
 struct folio_batch {
 	unsigned char nr;
+	unsigned char i;
 	bool percpu_pvec_drained;
 	struct folio *folios[PAGEVEC_SIZE];
 };
@@ -40,12 +41,14 @@ struct folio_batch {
 static inline void folio_batch_init(struct folio_batch *fbatch)
 {
 	fbatch->nr = 0;
+	fbatch->i = 0;
 	fbatch->percpu_pvec_drained = false;
 }
 
 static inline void folio_batch_reinit(struct folio_batch *fbatch)
 {
 	fbatch->nr = 0;
+	fbatch->i = 0;
 }
 
 static inline unsigned int folio_batch_count(struct folio_batch *fbatch)
@@ -75,6 +78,21 @@ static inline unsigned folio_batch_add(s
 	return folio_batch_space(fbatch);
 }
 
+/**
+ * folio_batch_next - Return the next folio to process.
+ * @fbatch: The folio batch being processed.
+ *
+ * Use this function to implement a queue of folios.
+ *
+ * Return: The next folio in the queue, or NULL if the queue is empty.
+ */
+static inline struct folio *folio_batch_next(struct folio_batch *fbatch)
+{
+	if (fbatch->i == fbatch->nr)
+		return NULL;
+	return fbatch->folios[fbatch->i++];
+}
+
 void __folio_batch_release(struct folio_batch *pvec);
 
 static inline void folio_batch_release(struct folio_batch *fbatch)
_

Patches currently in -mm which might be from willy@infradead.org are

memcg-convert-mem_cgroup_move_charge_pte_range-to-use-a-folio.patch
memcg-return-the-folio-in-union-mc_target.patch
memcg-use-a-folio-in-get_mctgt_type.patch
memcg-use-a-folio-in-get_mctgt_type_thp.patch
mm-add-pfn_swap_entry_folio.patch
proc-use-pfn_swap_entry_folio-where-obvious.patch
mprotect-use-pfn_swap_entry_folio.patch
highmem-add-kernel-doc-for-memcpy__folio.patch
rmap-replace-two-calls-to-compound_order-with-folio_order.patch
writeback-remove-a-duplicate-prototype-for-tag_pages_for_writeback.patch
writeback-factor-folio_prepare_writeback-out-of-write_cache_pages.patch
writeback-factor-writeback_get_batch-out-of-write_cache_pages.patch
writeback-simplify-the-loops-in-write_cache_pages.patch
pagevec-add-ability-to-iterate-a-queue.patch
writeback-use-the-folio_batch-queue-iterator.patch
writeback-move-the-folio_prepare_writeback-loop-out-of-write_cache_pages.patch
writeback-remove-a-use-of-write_cache_pages-from-do_writepages.patch
bounds-support-non-power-of-two-config_nr_cpus.patch