[patch 01/16] Revert "mm: madvise: skip unmapped vma holes passed to process_madvise"

[Andrew Morton <akpm@linux-foundation.org>]

From: Charan Teja Kalla <quic_charante@quicinc.com>
Subject: Revert "mm: madvise: skip unmapped vma holes passed to process_madvise"

This reverts commit 08095d6310a7 ("mm: madvise: skip unmapped vma holes
passed to process_madvise") as process_madvise() fails to return the exact
processed bytes in other cases too.  As an example: if process_madvise()
hits mlocked pages after processing some initial bytes passed in [start,
end), it just returns EINVAL although 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.

Link: https://lkml.kernel.org/r/e73da1304a88b6a8a11907045117cccf4c2b8374.1648046642.git.quic_charante@quicinc.com
Fixes: 08095d6310a7ce ("mm: madvise: skip unmapped vma holes passed to process_madvise")
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/madvise.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

--- a/mm/madvise.c~revert-mm-madvise-skip-unmapped-vma-holes-passed-to-process_madvise
+++ a/mm/madvise.c
@@ -1464,16 +1464,9 @@ SYSCALL_DEFINE5(process_madvise, int, pi
 
 	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);
 	}
_