From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Subject: Re: [PATCH v2 3/7] mm/gup: remove vmas parameter from get_user_pages_remote()
Date: Sat, 15 Apr 2023 20:40:44 +0900 [thread overview]
Message-ID: <ba0be6a6-8b31-453c-5895-d502ba4d0f64@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <64ae6557-0e46-48a8-badd-af8993645330@lucifer.local>
On 2023/04/15 20:27, Lorenzo Stoakes wrote:
>>> @@ -5617,11 +5618,11 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
>>> bytes = PAGE_SIZE-offset;
>>>
>>> maddr = kmap(page);
>>> - if (write) {
>>> + if (write && vma) {
>>> copy_to_user_page(vma, page, addr,
>>> maddr + offset, buf, bytes);
>>> set_page_dirty_lock(page);
>>> - } else {
>>> + } else if (vma) {
>>> copy_from_user_page(vma, page, addr,
>>> buf, maddr + offset, bytes);
>>> }
>>
>> not calling copy_{from,to}_user_page() if vma == NULL is not sufficient for
>> propagating an error to caller.
>>
>
> This is a product of wanting to avoid churn, again this condition is simply
> impossible. Also as a pedantic side note - the loop explicitly indicates no
> errors are propagated, so there is no need to do so.
Since __access_remote_vm() implicitly indicates an error via "return buf - old_buf;",
"buf += bytes;" must not be executed if copy_{to,from}_user_page(bytes) was not called.
next prev parent reply other threads:[~2023-04-15 11:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-15 9:06 [PATCH v2 0/7] remove the vmas parameter from GUP APIs Lorenzo Stoakes
2023-04-15 9:07 ` [PATCH v2 1/7] mm/gup: remove unused vmas parameter from get_user_pages() Lorenzo Stoakes
2023-04-15 9:08 ` [PATCH v2 2/7] mm/gup: remove unused vmas parameter from pin_user_pages_remote() Lorenzo Stoakes
2023-04-15 9:08 ` [PATCH v2 3/7] mm/gup: remove vmas parameter from get_user_pages_remote() Lorenzo Stoakes
2023-04-15 9:52 ` Tetsuo Handa
2023-04-15 10:14 ` Lorenzo Stoakes
2023-04-15 10:36 ` Tetsuo Handa
2023-04-15 11:27 ` Lorenzo Stoakes
2023-04-15 11:40 ` Tetsuo Handa [this message]
2023-04-15 11:48 ` Lorenzo Stoakes
2023-04-15 9:08 ` [PATCH v2 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag Lorenzo Stoakes
2023-04-15 9:08 ` [PATCH v2 5/7] io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages() Lorenzo Stoakes
2023-04-15 9:08 ` [PATCH v2 6/7] mm/gup: remove vmas parameter from pin_user_pages() Lorenzo Stoakes
2023-04-15 9:09 ` [PATCH v2 7/7] mm/gup: remove vmas array from internal GUP functions Lorenzo Stoakes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ba0be6a6-8b31-453c-5895-d502ba4d0f64@I-love.SAKURA.ne.jp \
--to=penguin-kernel@i-love.sakura.ne.jp \
--cc=akpm@linux-foundation.org \
--cc=linux-mm@kvack.org \
--cc=lstoakes@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).