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

[Davidlohr Bueso]

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@xxxxxxxxxx>
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>

Acked-by: Davidlohr Bueso <dbueso@xxxxxxx>