linux-kernel - Re: [PATCH 3/6] fs: Convert block_read_full

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Message-ID: <20201022234011.GD3613750@gmail.com>
Date:   Thu, 22 Oct 2020 16:40:11 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-fscrypt@...r.kernel.org
Subject: Re: [PATCH 3/6] fs: Convert block_read_full_page to be synchronous

On Thu, Oct 22, 2020 at 10:22:25PM +0100, Matthew Wilcox (Oracle) wrote:
> +static int readpage_submit_bhs(struct page *page, struct blk_completion *cmpl,
> +		unsigned int nr, struct buffer_head **bhs)
> +{
> +	struct bio *bio = NULL;
> +	unsigned int i;
> +	int err;
> +
> +	blk_completion_init(cmpl, nr);
> +
> +	for (i = 0; i < nr; i++) {
> +		struct buffer_head *bh = bhs[i];
> +		sector_t sector = bh->b_blocknr * (bh->b_size >> 9);
> +		bool same_page;
> +
> +		if (buffer_uptodate(bh)) {
> +			end_buffer_async_read(bh, 1);
> +			blk_completion_sub(cmpl, BLK_STS_OK, 1);
> +			continue;
> +		}
> +		if (bio) {
> +			if (bio_end_sector(bio) == sector &&
> +			    __bio_try_merge_page(bio, bh->b_page, bh->b_size,
> +					bh_offset(bh), &same_page))
> +				continue;
> +			submit_bio(bio);
> +		}
> +		bio = bio_alloc(GFP_NOIO, 1);
> +		bio_set_dev(bio, bh->b_bdev);
> +		bio->bi_iter.bi_sector = sector;
> +		bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
> +		bio->bi_end_io = readpage_end_bio;
> +		bio->bi_private = cmpl;
> +		/* Take care of bh's that straddle the end of the device */
> +		guard_bio_eod(bio);
> +	}

The following is needed to set the bio encryption context for the
'-o inlinecrypt' case on ext4:

diff --git a/fs/buffer.c b/fs/buffer.c
index 95c338e2b99c..546a08c5003b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2237,6 +2237,7 @@ static int readpage_submit_bhs(struct page *page, struct blk_completion *cmpl,
 			submit_bio(bio);
 		}
 		bio = bio_alloc(GFP_NOIO, 1);
+		fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
 		bio_set_dev(bio, bh->b_bdev);
 		bio->bi_iter.bi_sector = sector;
 		bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));