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Mon, 7 Apr 2025 03:03:41 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (unknown [10.72.112.15]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D41EF1801752; Mon, 7 Apr 2025 03:03:35 +0000 (UTC) From: Baoquan He To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, osalvador@suse.de, david@redhat.com, mingo@kernel.org, yanjun.zhu@linux.dev, linux-kernel@vger.kernel.org, Baoquan He Subject: [PATCH v3 2/3] mm/gup: remove unneeded checking in follow_page_pte() Date: Mon, 7 Apr 2025 11:03:05 +0800 Message-ID: <20250407030306.411977-3-bhe@redhat.com> In-Reply-To: <20250407030306.411977-1-bhe@redhat.com> References: <20250407030306.411977-1-bhe@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Queue-Id: 51CDFC0003 X-Stat-Signature: dx9wfrsh5tq5eotiyut35tair1kqgmnz X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1743995027-508189 X-HE-Meta: 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 31S0nCNv Lu4VAno02tilLnWIx9rnjIvTOUnB+amV1P5DdcWN+dIK2TNSXsBrjvsTwCPE2AX9d7xNikzTQ7p990zuVsTijzG8Bdj7Uf4GSuntaGuvA6BhcuXo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: In __get_user_pages(), it will traverse page table and take a reference to the page the given user address corresponds to if GUP_GET or GUP_PIN is set. However, it's not supported both GUP_GET and GUP_PIN are set. Even though this check need be done, it should be done earlier, but not doing it till entering into follow_page_pte() and failed. Furthermore, this checking has been done in is_valid_gup_args() and all external users of __get_user_pages() will call is_valid_gup_args() to catch the illegal setting. We don't need to worry about internal users of __get_user_pages() because the gup_flags are set by MM code correctly. Here remove the checking in follow_page_pte(), and add VM_WARN_ON_ONCE() to catch the possible exceptional setting just in case. And also change the VM_BUG_ON to VM_WARN_ON_ONCE() for checking (!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))) because the checking has been done in is_valid_gup_args() for external users of __get_user_pages(). Signed-off-by: Baoquan He Reviewed-by: Oscar Salvador Acked-by: David Hildenbrand --- mm/gup.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 67a7de9e4f80..5b3ac5a867a3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -844,11 +844,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, pte_t *ptep, pte; int ret; - /* FOLL_GET and FOLL_PIN are mutually exclusive. */ - if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == - (FOLL_PIN | FOLL_GET))) - return ERR_PTR(-EINVAL); - ptep = pte_offset_map_lock(mm, pmd, address, &ptl); if (!ptep) return no_page_table(vma, flags, address); @@ -1432,7 +1427,11 @@ static long __get_user_pages(struct mm_struct *mm, start = untagged_addr_remote(mm, start); - VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); + VM_WARN_ON_ONCE(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + VM_WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET)); do { struct page *page;