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From:   Charan Teja Kalla <quic_charante@quicinc.com>
To:     <akpm@linux-foundation.org>, <mhocko@suse.com>,
        <minchan@kernel.org>, <surenb@google.com>, <vbabka@suse.cz>,
        <rientjes@google.com>, <nadav.amit@gmail.com>,
        <edgararriaga@google.com>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Charan Teja Kalla <quic_charante@quicinc.com>
Subject: [PATCH 1/2] Revert "mm: madvise: skip unmapped vma holes passed to process_madvise"
Date:   Wed, 23 Mar 2022 20:54:09 +0530
Message-ID: <e73da1304a88b6a8a11907045117cccf4c2b8374.1648046642.git.quic_charante@quicinc.com>
In-Reply-To: <cover.1648046642.git.quic_charante@quicinc.com>
References: <cover.1648046642.git.quic_charante@quicinc.com>
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This reverts commit 08095d6310a7 ("mm: madvise: skip unmapped vma holes
passed to process_madvise") as process_madvise() fails to return exact
processed bytes at other cases too. As an example: if the
process_madvise() hits mlocked pages after processing some initial bytes
passed in [start, end), it just returns EINVAL though some bytes are
processed. Thus making an exception only for ENOMEM is partially fixing
the problem of returning the proper advised bytes.

Thus revert this patch and return proper bytes advised, if there any,
for all the error types in the following patch.

Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
---
 mm/madvise.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 39b712f..0d8fd17 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1433,16 +1433,9 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
 
 	while (iov_iter_count(&iter)) {
 		iovec = iov_iter_iovec(&iter);
-		/*
-		 * do_madvise returns ENOMEM if unmapped holes are present
-		 * in the passed VMA. process_madvise() is expected to skip
-		 * unmapped holes passed to it in the 'struct iovec' list
-		 * and not fail because of them. Thus treat -ENOMEM return
-		 * from do_madvise as valid and continue processing.
-		 */
 		ret = do_madvise(mm, (unsigned long)iovec.iov_base,
 					iovec.iov_len, behavior);
-		if (ret < 0 && ret != -ENOMEM)
+		if (ret < 0)
 			break;
 		iov_iter_advance(&iter, iovec.iov_len);
 	}
-- 
2.7.4