linux-kernel - Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm

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Message-ID: <20180730164459.zduhnk7itoldqnom@linux-r8p5>
Date:   Mon, 30 Jul 2018 09:44:59 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Jane Chu <jane.chu@...cle.com>
Cc:     akpm@...ux-foundation.org, dan.j.williams@...el.com,
        mhocko@...e.com, jack@...e.cz, jglisse@...hat.com,
        mike.kravetz@...cle.com, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm_ops

On Fri, 27 Jul 2018, Jane Chu wrote:

>Commit 05ea88608d4e13 (mm, hugetlbfs: introduce ->pagesize() to
>vm_operations_struct) adds a new ->pagesize() function to
>hugetlb_vm_ops, intended to cover all hugetlbfs backed files.
>
>With System V shared memory model, if "huge page" is specified,
>the "shared memory" is backed by hugetlbfs files, but the mappings
>initiated via shmget/shmat have their original vm_ops overwritten
>with shm_vm_ops, so we need to add a ->pagesize function to shm_vm_ops.
>Otherwise, vma_kernel_pagesize() returns PAGE_SIZE given a hugetlbfs
>backed vma, result in below BUG:
>
>fs/hugetlbfs/inode.c
>        443             if (unlikely(page_mapped(page))) {
>        444                     BUG_ON(truncate_op);
>
>[  242.268342] hugetlbfs: oracle (4592): Using mlock ulimits for SHM_HUGETLB is deprecated
>[  282.653208] ------------[ cut here ]------------
>[  282.708447] kernel BUG at fs/hugetlbfs/inode.c:444!
>[  282.818957] Modules linked in: nfsv3 rpcsec_gss_krb5 nfsv4 ...
>[  284.025873] CPU: 35 PID: 5583 Comm: oracle_5583_sbt Not tainted 4.14.35-1829.el7uek.x86_64 #2
>[  284.246609] task: ffff9bf0507aaf80 task.stack: ffffa9e625628000
>[  284.317455] RIP: 0010:remove_inode_hugepages+0x3db/0x3e2
>....
>[  285.292389] Call Trace:
>[  285.321630]  hugetlbfs_evict_inode+0x1e/0x3e
>[  285.372707]  evict+0xdb/0x1af
>[  285.408185]  iput+0x1a2/0x1f7
>[  285.443661]  dentry_unlink_inode+0xc6/0xf0
>[  285.492661]  __dentry_kill+0xd8/0x18d
>[  285.536459]  dput+0x1b5/0x1ed
>[  285.571939]  __fput+0x18b/0x216
>[  285.609495]  ____fput+0xe/0x10
>[  285.646030]  task_work_run+0x90/0xa7
>[  285.688788]  exit_to_usermode_loop+0xdd/0x116
>[  285.740905]  do_syscall_64+0x187/0x1ae
>[  285.785740]  entry_SYSCALL_64_after_hwframe+0x150/0x0
>
>Suggested-by: Mike Kravetz <mike.kravetz@...cle.com>
>Signed-off-by: Jane Chu <jane.chu@...cle.com>

Acked-by: Davidlohr Bueso <dbueso@...e.de>