From 6ad7c607b125ce02bd0870f490d990aee8609070 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Fri, 15 Dec 2023 20:02:34 +0000 Subject: fs: reduce stack usage in __mpage_writepage 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/20231215200245.748418-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: Jens Axboe Signed-off-by: Andrew Morton --- fs/mpage.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) (limited to 'fs/mpage.c') diff --git a/fs/mpage.c b/fs/mpage.c index 630f4a7c7d03..84b02098e7a5 100644 --- a/fs/mpage.c +++ b/fs/mpage.c @@ -466,7 +466,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc, const unsigned blocks_per_page = PAGE_SIZE >> blkbits; sector_t last_block; sector_t block_in_file; - sector_t blocks[MAX_BUF_PER_PAGE]; + sector_t first_block; unsigned page_block; unsigned first_unmapped = blocks_per_page; struct block_device *bdev = NULL; @@ -504,10 +504,12 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc, if (!buffer_dirty(bh) || !buffer_uptodate(bh)) goto confused; if (page_block) { - if (bh->b_blocknr != blocks[page_block-1] + 1) + if (bh->b_blocknr != first_block + page_block) goto confused; + } else { + first_block = bh->b_blocknr; } - blocks[page_block++] = bh->b_blocknr; + page_block++; boundary = buffer_boundary(bh); if (boundary) { boundary_block = bh->b_blocknr; @@ -556,10 +558,12 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc, boundary_bdev = map_bh.b_bdev; } if (page_block) { - if (map_bh.b_blocknr != blocks[page_block-1] + 1) + if (map_bh.b_blocknr != first_block + page_block) goto confused; + } else { + first_block = map_bh.b_blocknr; } - blocks[page_block++] = map_bh.b_blocknr; + page_block++; boundary = buffer_boundary(&map_bh); bdev = map_bh.b_bdev; if (block_in_file == last_block) @@ -591,7 +595,7 @@ page_is_mapped: /* * This page will go to BIO. Do we need to send this BIO off first? */ - if (bio && mpd->last_block_in_bio != blocks[0] - 1) + if (bio && mpd->last_block_in_bio != first_block - 1) bio = mpage_bio_submit_write(bio); alloc_new: @@ -599,7 +603,7 @@ alloc_new: bio = bio_alloc(bdev, BIO_MAX_VECS, REQ_OP_WRITE | wbc_to_write_flags(wbc), GFP_NOFS); - bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); + bio->bi_iter.bi_sector = first_block << (blkbits - 9); wbc_init_bio(wbc, bio); } @@ -627,7 +631,7 @@ alloc_new: boundary_block, 1 << blkbits); } } else { - mpd->last_block_in_bio = blocks[blocks_per_page - 1]; + mpd->last_block_in_bio = first_block + blocks_per_page - 1; } goto out; -- cgit