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

[Jane Chu]

Hi, Davidlohr,

On 7/30/2018 9:44 AM, Davidlohr Bueso wrote:

> 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
> > ÂÂÂÂÂÂ 443ÂÂÂÂÂÂÂÂÂÂÂÂ if (unlikely(page_mapped(page))) {
> > ÂÂÂÂÂÂ 444ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ BUG_ON(truncate_op);
> >
> > [Â 242.268342] hugetlbfs: oracle (4592): Using mlock ulimits for 
> > SHM_HUGETLB is deprecated
> > [Â 282.653208] ------------[ cut here ]------------
> > [Â 282.708447] kernel BUG at fs/hugetlbfs/inode.c:444!
> > [Â 282.818957] Modules linked in: nfsv3 rpcsec_gss_krb5 nfsv4 ...
> > [Â 284.025873] CPU: 35 PID: 5583 Comm: oracle_5583_sbt Not tainted 
> > 4.14.35-1829.el7uek.x86_64 #2
> > [Â 284.246609] task: ffff9bf0507aaf80 task.stack: ffffa9e625628000
> > [Â 284.317455] RIP: 0010:remove_inode_hugepages+0x3db/0x3e2
> > ....
> > [Â 285.292389] Call Trace:
> > [Â 285.321630]Â hugetlbfs_evict_inode+0x1e/0x3e
> > [Â 285.372707]Â evict+0xdb/0x1af
> > [Â 285.408185]Â iput+0x1a2/0x1f7
> > [Â 285.443661]Â dentry_unlink_inode+0xc6/0xf0
> > [Â 285.492661]Â __dentry_kill+0xd8/0x18d
> > [Â 285.536459]Â dput+0x1b5/0x1ed
> > [Â 285.571939]Â __fput+0x18b/0x216
> > [Â 285.609495]Â ____fput+0xe/0x10
> > [Â 285.646030]Â task_work_run+0x90/0xa7
> > [Â 285.688788]Â exit_to_usermode_loop+0xdd/0x116
> > [Â 285.740905]Â do_syscall_64+0x187/0x1ae
> > [Â 285.785740]Â entry_SYSCALL_64_after_hwframe+0x150/0x0
> >
> > Suggested-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
>
> Acked-by: Davidlohr Bueso <dbueso@xxxxxxx>

Thank you!

-jane