From: Michal Hocko <mhocko@suse.com>
To: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: akpm@linux-foundation.org, surenb@google.com, vbabka@suse.cz,
rientjes@google.com, sfr@canb.auug.org.au,
edgararriaga@google.com, minchan@kernel.org,
nadav.amit@gmail.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
"# 5 . 10+" <stable@vger.kernel.org>
Subject: Re: [PATCH V2,1/2] mm: madvise: return correct bytes advised with process_madvise
Date: Mon, 21 Mar 2022 16:18:18 +0100 [thread overview]
Message-ID: <YjiXOmbO9bn1r/wC@dhcp22.suse.cz> (raw)
In-Reply-To: <125b61a0edcee5c2db8658aed9d06a43a19ccafc.1647008754.git.quic_charante@quicinc.com>
On Fri 11-03-22 20:59:05, Charan Teja Kalla wrote:
> The process_madvise() system call returns error even after processing
> some VMA's passed in the 'struct iovec' vector list which leaves the
> user confused to know where to restart the advise next. It is also
> against this syscall man page[1] documentation where it mentions that
> "return value may be less than the total number of requested bytes, if
> an error occurred after some iovec elements were already processed.".
>
> Consider a user passed 10 VMA's in the 'struct iovec' vector list of
> which 9 are processed but one. Then it just returns the error caused on
> that failed VMA despite the first 9 VMA's processed, leaving the user
> confused about on which VMA it is failed. Returning the number of bytes
> processed here can help the user to know which VMA it is failed on and
> thus can retry/skip the advise on that VMA.
>
> [1]https://man7.org/linux/man-pages/man2/process_madvise.2.html.
>
> Fixes: ecb8ac8b1f14("mm/madvise: introduce process_madvise() syscall: an external memory hinting API")
> Cc: <stable@vger.kernel.org> # 5.10+
> Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> Changes in V2:
> -- Separated the ENOMEM handling and return bytes processed, as per Minchan comments.
> -- This contains correcting return bytes processed with process_madvise().
>
> Changes in V1:
> -- Fixed the ENOMEM handling and return bytes processed by process_madvise.
> -- https://patchwork.kernel.org/project/linux-mm/patch/1646803679-11433-1-git-send-email-quic_charante@quicinc.com/
>
> mm/madvise.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 38d0f51..e97e6a9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1433,8 +1433,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> iov_iter_advance(&iter, iovec.iov_len);
> }
>
> - if (ret == 0)
> - ret = total_len - iov_iter_count(&iter);
> + ret = (total_len - iov_iter_count(&iter)) ? : ret;
>
> release_mm:
> mmput(mm);
> --
> 2.7.4
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2022-03-21 15:19 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 15:29 [PATCH V2,0/2]mm: madvise: return correct bytes processed with process_madvise Charan Teja Kalla
2022-03-11 15:29 ` [PATCH V2,1/2] mm: madvise: return correct bytes advised " Charan Teja Kalla
2022-03-15 22:20 ` Minchan Kim
2022-03-21 15:18 ` Michal Hocko [this message]
2022-03-11 15:29 ` [PATCH V2,2/2] mm: madvise: skip unmapped vma holes passed to process_madvise Charan Teja Kalla
2022-03-15 22:58 ` Minchan Kim
2022-03-15 23:48 ` Andrew Morton
2022-03-16 1:43 ` Minchan Kim
2022-03-16 14:19 ` Charan Teja Kalla
2022-03-16 21:29 ` Andrew Morton
2022-03-17 16:28 ` Minchan Kim
2022-03-17 16:53 ` Suren Baghdasaryan
2022-03-17 20:38 ` Nadav Amit
2022-03-18 14:05 ` Charan Teja Kalla
2022-03-18 15:37 ` Minchan Kim
2022-03-17 16:24 ` Minchan Kim
2022-03-21 15:02 ` Michal Hocko
2022-03-22 5:19 ` Charan Teja Kalla
2022-03-21 15:34 ` Michal Hocko
2022-03-22 7:10 ` Charan Teja Kalla
2022-03-22 8:40 ` Michal Hocko
2022-03-11 21:42 ` [PATCH V2,0/2]mm: madvise: return correct bytes processed with process_madvise Andrew Morton
2022-03-15 14:26 ` Charan Teja Kalla
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