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[100.36.248.188]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-516d8c91f26sm80087331cf.18.2026.05.24.19.20.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 24 May 2026 19:20:45 -0700 (PDT) Date: Sun, 24 May 2026 22:20:43 -0400 From: Gregory Price To: Oleg Nesterov Cc: Alistair Popple , Andrew Morton , Byungchul Park , David Hildenbrand , Joshua Hahn , Matthew Brost , Rakie Kim , Ying Huang , Zi Yan , Jann Horn , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] mm/mempolicy: kernel_migrate_pages: simplify the usage of put_task_struct() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6A77620002 X-Stat-Signature: gm845apxtr6k8yionbe9ax4wnon3gr7i X-HE-Tag: 1779675646-903286 X-HE-Meta: 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 HokTqaqB nU7b5a59rfAU8zc8nibsLZr+1jFZEn0ZipeqasJa7AysY0/CO0sHPElNjEr22yith11moiQwxHtcb46zjp4MnBE6M+pHO0NtdgztaUXDcdh6fwmQS6vJqFlMvMJsGPd3mDjPsaMJAA/BXM9qzvIxMjObRiqes2P7sQVOl/8j4J/qrslzwYgnL7KxoHVtYix0n5gz7KaQBUVlnzWiO5/LcSV3e3Cc7w+3LY1Oym35OGJUbFH07wlYiVeI14SOP/swLO+ze5b8ldn1IOSreizo1rOx8xXukYb98WfZ/L1q+alLEtzzjYEN5s3LoOQYlnv+oAI4yYXYuwNmgmhNfO7nLPKwymRg35i8+IjdWe1uGQCQ7kXg0njBsujHlQCeVVp5mJOZIPAWlIo0Y/eMz/kPUeoMCJMeWktHU7p9+Q+RW08Fwi7BLVhHMTNVLhh4U25rVyXQmGLZv+3RPFlkJqJIikftx69y0nnHy+4C9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, May 24, 2026 at 06:57:59PM +0200, Oleg Nesterov wrote: > kernel_migrate_pages() calls put_task_struct() twice; this complicates the > code. Move put_task_struct() to the unified exit path. This also allows us > to move the "out_put" label up and avoid another goto. > > Signed-off-by: Oleg Nesterov > --- > mm/mempolicy.c | 11 +++-------- > 1 file changed, 3 insertions(+), 8 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 4e4421b22b59..4326dff16aa6 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1922,25 +1922,20 @@ static int kernel_migrate_pages(pid_t pid, unsigned long maxnode, > goto out_put; > > mm = get_task_mm(task); > - put_task_struct(task); > - Hm, I was a little trigger-happy on that review, I just realized that this increases the scope in which there is a task reference held (i.e. we're now holding a reference across do_migrate_pages()) I don't *think* that's an issue, but it might we worth looking at the changelog to see if this was done intentionally. > if (!mm) { > err = -EINVAL; > - goto out; > + goto out_put; > } > > err = do_migrate_pages(mm, old, new, > capable(CAP_SYS_NICE) ? MPOL_MF_MOVE_ALL : MPOL_MF_MOVE); > > mmput(mm); > +out_put: > + put_task_struct(task); > out: > NODEMASK_SCRATCH_FREE(scratch); > - > return err; > - > -out_put: > - put_task_struct(task); > - goto out; > } > > SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, > -- > 2.52.0 >