From 5500221ea1b72c550b61f88fe3e8afbb08445989 Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Thu, 31 Oct 2019 17:23:15 +0800 Subject: [PATCH] ext4: bio_alloc with __GFP_DIRECT_RECLAIM never fails Similar to [1] [2], bio_alloc with __GFP_DIRECT_RECLAIM flags guarantees bio allocation under some given restrictions, as stated in block/bio.c and fs/direct-io.c So here it's ok to not check for NULL value from bio_alloc(). [1] https://lore.kernel.org/r/20191030035518.65477-1-gaoxiang25@huawei.com [2] https://lore.kernel.org/r/20190830162812.GA10694@infradead.org Cc: Theodore Ts'o Cc: Andreas Dilger Cc: Ritesh Harjani Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Link: https://lore.kernel.org/r/20191031092315.139267-1-gaoxiang25@huawei.com Signed-off-by: Theodore Ts'o --- fs/ext4/page-io.c | 57 ++++++++++++++++++---------------------------- fs/ext4/readpage.c | 6 +++-- 2 files changed, 26 insertions(+), 37 deletions(-) diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 893913d1c2fe..24aeedb8fc75 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -394,14 +394,16 @@ void ext4_io_submit_init(struct ext4_io_submit *io, io->io_end = NULL; } -static int io_submit_init_bio(struct ext4_io_submit *io, - struct buffer_head *bh) +static void io_submit_init_bio(struct ext4_io_submit *io, + struct buffer_head *bh) { struct bio *bio; + /* + * bio_alloc will _always_ be able to allocate a bio if + * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset(). + */ bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES); - if (!bio) - return -ENOMEM; bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9); bio_set_dev(bio, bh->b_bdev); bio->bi_end_io = ext4_end_bio; @@ -409,13 +411,12 @@ static int io_submit_init_bio(struct ext4_io_submit *io, io->io_bio = bio; io->io_next_block = bh->b_blocknr; wbc_init_bio(io->io_wbc, bio); - return 0; } -static int io_submit_add_bh(struct ext4_io_submit *io, - struct inode *inode, - struct page *page, - struct buffer_head *bh) +static void io_submit_add_bh(struct ext4_io_submit *io, + struct inode *inode, + struct page *page, + struct buffer_head *bh) { int ret; @@ -424,9 +425,7 @@ static int io_submit_add_bh(struct ext4_io_submit *io, ext4_io_submit(io); } if (io->io_bio == NULL) { - ret = io_submit_init_bio(io, bh); - if (ret) - return ret; + io_submit_init_bio(io, bh); io->io_bio->bi_write_hint = inode->i_write_hint; } ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh)); @@ -434,7 +433,6 @@ static int io_submit_add_bh(struct ext4_io_submit *io, goto submit_and_retry; wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size); io->io_next_block++; - return 0; } int ext4_bio_write_page(struct ext4_io_submit *io, @@ -527,8 +525,14 @@ int ext4_bio_write_page(struct ext4_io_submit *io, gfp_flags |= __GFP_NOFAIL; goto retry_encrypt; } - bounce_page = NULL; - goto out; + + printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret); + redirty_page_for_writepage(wbc, page); + do { + clear_buffer_async_write(bh); + bh = bh->b_this_page; + } while (bh != head); + goto unlock; } } @@ -536,30 +540,13 @@ int ext4_bio_write_page(struct ext4_io_submit *io, do { if (!buffer_async_write(bh)) continue; - ret = io_submit_add_bh(io, inode, bounce_page ?: page, bh); - if (ret) { - /* - * We only get here on ENOMEM. Not much else - * we can do but mark the page as dirty, and - * better luck next time. - */ - break; - } + io_submit_add_bh(io, inode, + bounce_page ? bounce_page : page, bh); nr_submitted++; clear_buffer_dirty(bh); } while ((bh = bh->b_this_page) != head); - /* Error stopped previous loop? Clean up buffers... */ - if (ret) { - out: - fscrypt_free_bounce_page(bounce_page); - printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret); - redirty_page_for_writepage(wbc, page); - do { - clear_buffer_async_write(bh); - bh = bh->b_this_page; - } while (bh != head); - } +unlock: unlock_page(page); /* Nothing submitted - we have to end page writeback */ if (!nr_submitted) diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c index a30b203fa461..fef7755300c3 100644 --- a/fs/ext4/readpage.c +++ b/fs/ext4/readpage.c @@ -360,10 +360,12 @@ int ext4_mpage_readpages(struct address_space *mapping, if (bio == NULL) { struct bio_post_read_ctx *ctx; + /* + * bio_alloc will _always_ be able to allocate a bio if + * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset(). + */ bio = bio_alloc(GFP_KERNEL, min_t(int, nr_pages, BIO_MAX_PAGES)); - if (!bio) - goto set_error_page; ctx = get_bio_post_read_ctx(inode, bio, page->index); if (IS_ERR(ctx)) { bio_put(bio);