From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 30 Jul 2018 10:58:51 +0200 From: Michal Hocko Subject: Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm_ops Message-ID: <20180730085851.GB24267@dhcp22.suse.cz> References: <20180727211727.5020-1-jane.chu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180727211727.5020-1-jane.chu@oracle.com> Sender: owner-linux-mm@kvack.org To: Jane Chu Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, jack@suse.cz, jglisse@redhat.com, mike.kravetz@oracle.com, dave@stgolabs.net, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org List-ID: On Fri 27-07-18 15:17:27, 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 > Signed-off-by: Jane Chu Acked-by: Michal Hocko with Cc: stable and Fixes: tag as suggested by Mike. I also agree with Matthew that the comment should be associated with hugetlb_vm_ops/shm_vm_ops. Thanks! > --- > include/linux/mm.h | 7 +++++++ > ipc/shm.c | 12 ++++++++++++ > 2 files changed, 19 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a0fbb9ffe380..0c759379f2d9 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -387,6 +387,13 @@ enum page_entry_size { > * These are the virtual MM functions - opening of an area, closing and > * unmapping it (needed to keep files on disk up-to-date etc), pointer > * to the functions called when a no-page or a wp-page exception occurs. > + * > + * Note, when a new function is introduced to vm_operations_struct and > + * added to hugetlb_vm_ops, please consider adding the function to > + * shm_vm_ops. This is because under System V memory model, though > + * mappings created via shmget/shmat with "huge page" specified are > + * backed by hugetlbfs files, their original vm_ops are overwritten with > + * shm_vm_ops. > */ > struct vm_operations_struct { > void (*open)(struct vm_area_struct * area); > diff --git a/ipc/shm.c b/ipc/shm.c > index 051a3e1fb8df..fefa00d310fb 100644 > --- a/ipc/shm.c > +++ b/ipc/shm.c > @@ -427,6 +427,17 @@ static int shm_split(struct vm_area_struct *vma, unsigned long addr) > return 0; > } > > +static unsigned long shm_pagesize(struct vm_area_struct *vma) > +{ > + struct file *file = vma->vm_file; > + struct shm_file_data *sfd = shm_file_data(file); > + > + if (sfd->vm_ops->pagesize) > + return sfd->vm_ops->pagesize(vma); > + > + return PAGE_SIZE; > +} > + > #ifdef CONFIG_NUMA > static int shm_set_policy(struct vm_area_struct *vma, struct mempolicy *new) > { > @@ -554,6 +565,7 @@ static const struct vm_operations_struct shm_vm_ops = { > .close = shm_close, /* callback for when the vm-area is released */ > .fault = shm_fault, > .split = shm_split, > + .pagesize = shm_pagesize, > #if defined(CONFIG_NUMA) > .set_policy = shm_set_policy, > .get_policy = shm_get_policy, > -- > 2.15.GIT > -- Michal Hocko SUSE Labs