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.
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
include/linux/swap.h | 4 ++--
mm/swapfile.c | 15 ++++++---------
2 files changed, 8 insertions(+), 11 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 8772132d21dc..e1f3201dec6f 100644
--- a/include/linux/swap.h
+++ b/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.
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7ead5fb96d9d..b3f977d9c83e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2225,8 +2225,8 @@ 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.
@@ -2234,12 +2234,12 @@ 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.
*
@@ -2248,10 +2248,7 @@ 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)
{
--
2.23.0
