[PATCH 02/11] fscrypt: keep multiple bios in flight in fscrypt_zeroout_range_inline_crypt

[Christoph Hellwig <hch@lst.de>]

This should slightly improve performance for large zeroing operations,
but more importantly prepares for blk-crypto refactoring that requires
all fscrypt users to call submit_bio directly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
---
 fs/crypto/bio.c | 86 +++++++++++++++++++++++++++++++------------------
 1 file changed, 54 insertions(+), 32 deletions(-)

diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
index 68b0424d879a..c2b3ca100f8d 100644
--- a/fs/crypto/bio.c
+++ b/fs/crypto/bio.c
@@ -47,49 +47,71 @@ bool fscrypt_decrypt_bio(struct bio *bio)
 }
 EXPORT_SYMBOL(fscrypt_decrypt_bio);
 
+struct fscrypt_zero_done {
+	atomic_t		pending;
+	blk_status_t		status;
+	struct completion	done;
+};
+
+static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done)
+{
+	if (atomic_dec_and_test(&done->pending))
+		complete(&done->done);
+}
+
+static void fscrypt_zeroout_range_end_io(struct bio *bio)
+{
+	struct fscrypt_zero_done *done = bio->bi_private;
+
+	if (bio->bi_status)
+		cmpxchg(&done->status, 0, bio->bi_status);
+	fscrypt_zeroout_range_done(done);
+	bio_put(bio);
+}
+
 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
 					      pgoff_t lblk, sector_t sector,
 					      unsigned int len)
 {
 	const unsigned int blockbits = inode->i_blkbits;
 	const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
-	struct bio *bio;
-	int ret, err = 0;
-	int num_pages = 0;
-
-	/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
-	bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
-			GFP_NOFS);
+	struct fscrypt_zero_done done = {
+		.pending	= ATOMIC_INIT(1),
+		.done		= COMPLETION_INITIALIZER_ONSTACK(done.done),
+	};
 
 	while (len) {
-		unsigned int blocks_this_page = min(len, blocks_per_page);
-		unsigned int bytes_this_page = blocks_this_page << blockbits;
+		struct bio *bio;
+		unsigned int n;
 
-		if (num_pages == 0) {
-			fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
-			bio->bi_iter.bi_sector = sector;
-		}
-		ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
-		if (WARN_ON_ONCE(ret != bytes_this_page)) {
-			err = -EIO;
-			goto out;
-		}
-		num_pages++;
-		len -= blocks_this_page;
-		lblk += blocks_this_page;
-		sector += (bytes_this_page >> SECTOR_SHIFT);
-		if (num_pages == BIO_MAX_VECS || !len ||
-		    !fscrypt_mergeable_bio(bio, inode, lblk)) {
-			err = submit_bio_wait(bio);
-			if (err)
-				goto out;
-			bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
-			num_pages = 0;
+		bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
+				GFP_NOFS);
+		bio->bi_iter.bi_sector = sector;
+		bio->bi_private = &done;
+		bio->bi_end_io = fscrypt_zeroout_range_end_io;
+		fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
+
+		for (n = 0; n < BIO_MAX_VECS; n++) {
+			unsigned int blocks_this_page =
+				min(len, blocks_per_page);
+			unsigned int bytes_this_page = blocks_this_page << blockbits;
+
+			__bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
+			len -= blocks_this_page;
+			lblk += blocks_this_page;
+			sector += (bytes_this_page >> SECTOR_SHIFT);
+			if (!len || !fscrypt_mergeable_bio(bio, inode, lblk))
+				break;
 		}
+
+		atomic_inc(&done.pending);
+		submit_bio(bio);
 	}
-out:
-	bio_put(bio);
-	return err;
+
+	fscrypt_zeroout_range_done(&done);
+
+	wait_for_completion(&done.done);
+	return blk_status_to_errno(done.status);
 }
 
 /**
-- 
2.47.3