linux-kernel - [PATCH 5.9 295/391] block: advance iov_iter on bio_add_hw

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Date:   Tue,  3 Nov 2020 21:35:46 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Naohiro Aota <naohiro.aota@....com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.9 295/391] block: advance iov_iter on bio_add_hw_page failure

From: Naohiro Aota <naohiro.aota@....com>

commit 4977d121bc9bc5138d4d48b85469123001859573 upstream.

When the bio's size reaches max_append_sectors, bio_add_hw_page returns
0 then __bio_iov_append_get_pages returns -EINVAL. This is an expected
result of building a small enough bio not to be split in the IO path.
However, iov_iter is not advanced in this case, causing the same pages
are filled for the bio again and again.

Fix the case by properly advancing the iov_iter for already processed
pages.

Fixes: 0512a75b98f8 ("block: Introduce REQ_OP_ZONE_APPEND")
Cc: stable@...r.kernel.org # 5.8+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Signed-off-by: Naohiro Aota <naohiro.aota@....com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/bio.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/block/bio.c
+++ b/block/bio.c
@@ -1046,6 +1046,7 @@ static int __bio_iov_append_get_pages(st
 	ssize_t size, left;
 	unsigned len, i;
 	size_t offset;
+	int ret = 0;
 
 	if (WARN_ON_ONCE(!max_append_sectors))
 		return 0;
@@ -1068,15 +1069,17 @@ static int __bio_iov_append_get_pages(st
 
 		len = min_t(size_t, PAGE_SIZE - offset, left);
 		if (bio_add_hw_page(q, bio, page, len, offset,
-				max_append_sectors, &same_page) != len)
-			return -EINVAL;
+				max_append_sectors, &same_page) != len) {
+			ret = -EINVAL;
+			break;
+		}
 		if (same_page)
 			put_page(page);
 		offset = 0;
 	}
 
-	iov_iter_advance(iter, size);
-	return 0;
+	iov_iter_advance(iter, size - left);
+	return ret;
 }
 
 /**