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b=ImGibRl4GZlBpEsgk89z5akvxGngy7i/7SEdecQsQ4Y3z2LkRW68bkdabl77lARru 6Bwm4bS3xqNdn/tDbw7O74JBIrsqWEM8lL39w040M6BtrN94FBhJkBYsWAmrAmouUx YgPVuWE1RkPtPKVwJLkuOb+DYld/b7zxZe/Pnv8/lgBGcWNkchILygEPxbhtkC7Y8/ eViGATJVpH+o0/zdnO37KjpjmRH5VdRXsdVpavB6qpB687SbmJYdJLnmZIqlvJu/Gz nhT/eoEOkslbrsWb2Zh8muryP/dI0LGx7Tm4mx+bmpYD1dZJRZCmml/KGeqjoJAxzY 3eBXcY4sGjRqw== Date: Sun, 3 May 2026 10:48:36 +0200 From: Mike Rapoport To: Vineet Agarwal Cc: shuah@kernel.org, akpm@linux-foundation.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, surenb@google.com, mhocko@suse.com Subject: Re: [PATCH v2] selftests/mm: ksm-functional-tests: fix partial write handling Message-ID: References: <20260502005702.593878-1-agarwal.vineet2006@gmail.com> <20260503060234.644650-1-agarwal.vineet2006@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260503060234.644650-1-agarwal.vineet2006@gmail.com> X-Rspam-User: X-Rspamd-Queue-Id: 61337140004 X-Rspamd-Server: rspam04 X-Stat-Signature: pg71ijr1nkkwcem5d7egf3xbtb1ye8t7 X-HE-Tag: 1777798124-700228 X-HE-Meta: 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 dUh/gJdY cgjLBGN7UtGJFGwfVebNTGOXGQBR/l/ESwd0MkT9LBKTX8lrclAUQ9gqLIbJIn4x3gDJRJnMBp8vwGigpJCdgrOiNcxCU52klM8xBDZiDBAkdsDfU5Td4QVpbh8ut268Z/PUB0CUi0p04CJyihdi56yPaJcQzfbfRKe1fYrxht1qywvWioi35d5675M0HkvKSclUlXTPR7MpxQwQX0q5Sec1tPkLTsNhx8Lza4XyCK0l0ZmFvz4UnAqG4oR6OwYyRZofI/IuzFQEEGy/U0d5YkVUScVVBE7dsGrQ1wdY1v6l/y1V/LTlXQ+b47um+/QKDLzvCVD5sFPd2mffm/abhLtGKTRGms5zse4MDRpFZXmTEUqiGnLb5ihqNZhQF7LSyHN8g Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, May 03, 2026 at 11:30:30AM +0530, Vineet Agarwal wrote: > Update write() checks to properly detect and handle partial writes. > > Previously, partial writes (ret > 0 && ret != len) would return > -errno, but write() does not set errno in this case. This could > result in returning 0 and incorrectly signaling success. > > Fix this by: > - returning -errno only on actual failures (ret < 0) > - returning -EIO when a partial write is detected > > This ensures partial writes are treated as errors and prevents > false success reporting in tests. > > Signed-off-by: Vineet Agarwal > > Changes in v2: > - Fix incorrect use of -errno on partial writes > - Return -EIO when write() completes partially Please start a new thread for a new version of the patch. > --- > tools/testing/selftests/mm/ksm_functional_tests.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c > index 9a8c852acd68..c80254cda926 100644 > --- a/tools/testing/selftests/mm/ksm_functional_tests.c > +++ b/tools/testing/selftests/mm/ksm_functional_tests.c > @@ -507,9 +507,13 @@ static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) > if (write(ksm_fd, "1", 1) != 1) > return -errno; > > - ret = write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)); > - if (ret < 0 || ret != strlen(pages_to_scan)) > + ssize_t len = strlen(pages_to_scan); The v2 diff should be against the base, not against v1. > + > + ret = write(pages_to_scan_fd, pages_to_scan, len); > + if (ret < 0) > return -errno; > + if (ret != len) > + return -EIO; Just return -1 if write() != strlen(), the actual error code does not matter anyway. > ret = write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)); > if (ret < 0 || ret != strlen(sleep_ms)) > @@ -531,8 +535,10 @@ static int stop_ksmd_and_restore_frequency(void) > return -errno; > > ret = write(pages_to_scan_fd, "100", 3); > - if (ret < 0 || ret != 3) > + if (ret < 0) > return -errno; > + if (ret != 3) > + return -EIO; > > ret = write(sleep_millisecs_fd, "20", 2); > if (ret < 0 || ret != 2) > -- > 2.54.0 > -- Sincerely yours, Mike.