+ mm-swap-fix-comment-about-swap-extent.patch added to mm-unstable branch

+ mm-swap-fix-comment-about-swap-extent.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/swap: fix comment about swap extent
has been added to the -mm mm-unstable branch.  Its filename is
     mm-swap-fix-comment-about-swap-extent.patch

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

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------------------------------------------------------
From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/swap: fix comment about swap extent

Since commit 4efaceb1c5f8 ("mm, swap: use rbtree for swap_extent"), rbtree
is used for swap extent.  Also curr_swap_extent is removed at that time. 
Update the corresponding comment.

Link: https://lkml.kernel.org/r/20220509131416.17553-16-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/swap.h |    4 ++--
 mm/swapfile.c        |   15 ++++++---------
 2 files changed, 8 insertions(+), 11 deletions(-)

--- a/include/linux/swap.h~mm-swap-fix-comment-about-swap-extent
+++ a/include/linux/swap.h
@@ -173,8 +173,8 @@ struct zone;
 
 /*
  * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
- * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
- * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
+ * disk blocks.  A rbtree of swap extents maps the entire swapfile (Where the
+ * term `swapfile' refers to either a blockdevice or an IS_REG file). Apart
  * from setup, they're handled identically.
  *
  * We always assume that blocks are of size PAGE_SIZE.
--- a/mm/swapfile.c~mm-swap-fix-comment-about-swap-extent
+++ a/mm/swapfile.c
@@ -2224,8 +2224,8 @@ EXPORT_SYMBOL_GPL(add_swap_extent);
 
 /*
  * A `swap extent' is a simple thing which maps a contiguous range of pages
- * onto a contiguous range of disk blocks.  An ordered list of swap extents
- * is built at swapon time and is then used at swap_writepage/swap_readpage
+ * onto a contiguous range of disk blocks.  A rbtree of swap extents is
+ * built at swapon time and is then used at swap_writepage/swap_readpage
  * time for locating where on disk a page belongs.
  *
  * If the swapfile is an S_ISBLK block device, a single extent is installed.
@@ -2233,12 +2233,12 @@ EXPORT_SYMBOL_GPL(add_swap_extent);
  * swap files identically.
  *
  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
- * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
+ * extent rbtree operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
  * swapfiles are handled *identically* after swapon time.
  *
  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
- * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
- * some stray blocks are found which do not fall within the PAGE_SIZE alignment
+ * and will parse them into a rbtree, in PAGE_SIZE chunks.  If some stray
+ * blocks are found which do not fall within the PAGE_SIZE alignment
  * requirements, they are simply tossed out - we will never use those blocks
  * for swapping.
  *
@@ -2247,10 +2247,7 @@ EXPORT_SYMBOL_GPL(add_swap_extent);
  *
  * The amount of disk space which a single swap extent represents varies.
  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
- * extents in the list.  To avoid much list walking, we cache the previous
- * search location in `curr_swap_extent', and start new searches from there.
- * This is extremely effective.  The average number of iterations in
- * map_swap_page() has been measured at about 0.3 per page.  - akpm.
+ * extents in the rbtree. - akpm.
  */
 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
 {
_

Patches currently in -mm which might be from linmiaohe@huawei.com are

mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
mm-swapfile-fix-lost-swap-bits-in-unuse_pte.patch
mm-madvise-free-hwpoison-and-swapin-error-entry-in-madvise_free_pte_range.patch
mm-migration-reduce-the-rcu-lock-duration.patch
mm-migration-remove-unneeded-lock-page-and-pagemovable-check.patch
mm-migration-return-errno-when-isolate_huge_page-failed.patch
mm-migration-fix-potential-pte_unmap-on-an-not-mapped-pte.patch
mm-vmscan-take-min_slab_pages-into-account-when-try-to-call-shrink_node.patch
mm-vmscan-add-a-comment-about-madv_free-pages-check-in-folio_check_dirty_writeback.patch
mm-vmscan-introduce-helper-function-reclaim_page_list.patch
mm-vmscan-take-all-base-pages-of-thp-into-account-when-race-with-speculative-reference.patch
mm-vmscan-remove-obsolete-comment-in-kswapd_run.patch
mm-vmscan-use-helper-folio_is_file_lru.patch
mm-vmscan-use-helper-folio_is_file_lru-fix.patch
mm-z3fold-fix-sheduling-while-atomic.patch
mm-z3fold-fix-possible-null-pointer-dereferencing.patch
mm-z3fold-remove-buggy-use-of-stale-list-for-allocation.patch
mm-z3fold-throw-warning-on-failure-of-trylock_page-in-z3fold_alloc.patch
revert-mm-z3foldc-allow-__gfp_highmem-in-z3fold_alloc.patch
mm-z3fold-put-z3fold-page-back-into-unbuddied-list-when-reclaim-or-migration-fails.patch
mm-z3fold-always-clear-page_claimed-under-z3fold-page-lock.patch
mm-z3fold-fix-z3fold_reclaim_page-races-with-z3fold_free.patch
mm-z3fold-fix-z3fold_page_migrate-races-with-z3fold_map.patch
mm-swap-use-helper-is_swap_pte-in-swap_vma_readahead.patch
mm-swap-use-helper-macro-__attr_rw.patch
mm-swap-fold-__swap_info_get-into-its-sole-caller.patch
mm-swap-remove-unneeded-return-value-of-free_swap_slot.patch
mm-swap-print-bad-swap-offset-entry-in-get_swap_device.patch
mm-swap-remove-buggy-cache-nr-check-in-refill_swap_slots_cache.patch
mm-swap-remove-unneeded-p-=-null-check-in-__swap_duplicate.patch
mm-swap-make-page_swapcount-and-__lru_add_drain_all.patch
mm-swap-avoid-calling-swp_swap_info-when-try-to-check-swp_stable_writes.patch
mm-swap-add-helper-swap_offset_available.patch
mm-swap-fix-the-obsolete-comment-for-swp_type_shift.patch
mm-swap-clean-up-the-comment-of-find_next_to_unuse.patch
mm-swap-fix-the-comment-of-get_kernel_pages.patch
mm-swap-fix-comment-about-swap-extent.patch