The patch titled
Subject: fs: reduce stack usage in do_mpage_readpage
has been added to the -mm mm-unstable branch. Its filename is
fs-reduce-stack-usage-in-do_mpage_readpage.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-reduce-stack-usage-in-do_mpage_readpage.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@xxxxxxxxxxxxx>
Subject: fs: reduce stack usage in do_mpage_readpage
Date: Fri, 15 Dec 2023 20:02:35 +0000
Some architectures support a very large PAGE_SIZE, so instead of the 8
pointers we see with a 4kB PAGE_SIZE, we can see 128 pointers with 64kB or
so many on Hexagon that it trips compiler warnings about exceeding stack
frame size.
All we're doing with this array is checking for block contiguity, which we
can as well do by remembering the address of the first block in the page
and checking this block is at the appropriate offset from that address.
Link: https://lkml.kernel.org/r/20231215200245.748418-5-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/mpage.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/fs/mpage.c~fs-reduce-stack-usage-in-do_mpage_readpage
+++ a/fs/mpage.c
@@ -166,7 +166,7 @@ static struct bio *do_mpage_readpage(str
sector_t block_in_file;
sector_t last_block;
sector_t last_block_in_file;
- sector_t blocks[MAX_BUF_PER_PAGE];
+ sector_t first_block;
unsigned page_block;
unsigned first_hole = blocks_per_page;
struct block_device *bdev = NULL;
@@ -205,6 +205,7 @@ static struct bio *do_mpage_readpage(str
unsigned map_offset = block_in_file - args->first_logical_block;
unsigned last = nblocks - map_offset;
+ first_block = map_bh->b_blocknr + map_offset;
for (relative_block = 0; ; relative_block++) {
if (relative_block == last) {
clear_buffer_mapped(map_bh);
@@ -212,8 +213,6 @@ static struct bio *do_mpage_readpage(str
}
if (page_block == blocks_per_page)
break;
- blocks[page_block] = map_bh->b_blocknr + map_offset +
- relative_block;
page_block++;
block_in_file++;
}
@@ -259,7 +258,9 @@ static struct bio *do_mpage_readpage(str
goto confused; /* hole -> non-hole */
/* Contiguous blocks? */
- if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
+ if (!page_block)
+ first_block = map_bh->b_blocknr;
+ else if (first_block + page_block != map_bh->b_blocknr)
goto confused;
nblocks = map_bh->b_size >> blkbits;
for (relative_block = 0; ; relative_block++) {
@@ -268,7 +269,6 @@ static struct bio *do_mpage_readpage(str
break;
} else if (page_block == blocks_per_page)
break;
- blocks[page_block] = map_bh->b_blocknr+relative_block;
page_block++;
block_in_file++;
}
@@ -289,7 +289,7 @@ static struct bio *do_mpage_readpage(str
/*
* This folio will go to BIO. Do we need to send this BIO off first?
*/
- if (args->bio && (args->last_block_in_bio != blocks[0] - 1))
+ if (args->bio && (args->last_block_in_bio != first_block - 1))
args->bio = mpage_bio_submit_read(args->bio);
alloc_new:
@@ -298,7 +298,7 @@ alloc_new:
gfp);
if (args->bio == NULL)
goto confused;
- args->bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
+ args->bio->bi_iter.bi_sector = first_block << (blkbits - 9);
}
length = first_hole << blkbits;
@@ -313,7 +313,7 @@ alloc_new:
(first_hole != blocks_per_page))
args->bio = mpage_bio_submit_read(args->bio);
else
- args->last_block_in_bio = blocks[blocks_per_page - 1];
+ args->last_block_in_bio = first_block + blocks_per_page - 1;
out:
return args->bio;
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-memory-failure-pass-the-folio-and-the-page-to-collect_procs.patch
mm-memory-failure-check-the-mapcount-of-the-precise-page.patch
mm-memory-failure-cast-index-to-loff_t-before-shifting-it.patch
mailmap-add-an-old-address-for-naoya-horiguchi.patch
buffer-return-bool-from-grow_dev_folio.patch
buffer-calculate-block-number-inside-folio_init_buffers.patch
buffer-fix-grow_buffers-for-block-size-page_size.patch
buffer-cast-block-to-loff_t-before-shifting-it.patch
buffer-fix-various-functions-for-block-size-page_size.patch
buffer-handle-large-folios-in-__block_write_begin_int.patch
buffer-fix-more-functions-for-block-size-page_size.patch
mm-convert-ksm_might_need_to_copy-to-work-on-folios.patch
mm-convert-ksm_might_need_to_copy-to-work-on-folios-fix.patch
mm-remove-pageanonexclusive-assertions-in-unuse_pte.patch
mm-convert-unuse_pte-to-use-a-folio-throughout.patch
mm-remove-some-calls-to-page_add_new_anon_rmap.patch
mm-remove-stale-example-from-comment.patch
mm-remove-references-to-page_add_new_anon_rmap-in-comments.patch
mm-convert-migrate_vma_insert_page-to-use-a-folio.patch
mm-convert-collapse_huge_page-to-use-a-folio.patch
mm-remove-page_add_new_anon_rmap-and-lru_cache_add_inactive_or_unevictable.patch
mm-return-the-folio-from-__read_swap_cache_async.patch
mm-pass-a-folio-to-__swap_writepage.patch
mm-pass-a-folio-to-swap_writepage_fs.patch
mm-pass-a-folio-to-swap_writepage_bdev_sync.patch
mm-pass-a-folio-to-swap_writepage_bdev_async.patch
mm-pass-a-folio-to-swap_readpage_fs.patch
mm-pass-a-folio-to-swap_readpage_bdev_sync.patch
mm-pass-a-folio-to-swap_readpage_bdev_async.patch
mm-convert-swap_page_sector-to-swap_folio_sector.patch
mm-convert-swap_readpage-to-swap_read_folio.patch
mm-remove-page_swap_info.patch
mm-return-a-folio-from-read_swap_cache_async.patch
mm-convert-swap_cluster_readahead-and-swap_vma_readahead-to-return-a-folio.patch
fs-remove-clean_page_buffers.patch
fs-convert-clean_buffers-to-take-a-folio.patch
fs-reduce-stack-usage-in-__mpage_writepage.patch
fs-reduce-stack-usage-in-do_mpage_readpage.patch
adfs-remove-writepage-implementation.patch
bfs-remove-writepage-implementation.patch
hfs-really-remove-hfs_writepage.patch
hfsplus-really-remove-hfsplus_writepage.patch
minix-remove-writepage-implementation.patch
ocfs2-remove-writepage-implementation.patch
sysv-remove-writepage-implementation.patch
ufs-remove-writepage-implementation.patch
fs-convert-block_write_full_page-to-block_write_full_folio.patch
fs-remove-the-bh_end_io-argument-from-__block_write_full_folio.patch
