Messages in this thread | | | Subject | Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm_ops | From | Jane Chu <> | Date | Mon, 30 Jul 2018 20:07:57 -0700 |
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Hi, Michal,
On 7/30/2018 1:58 AM, Michal Hocko wrote: > 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 <mike.kravetz@oracle.com> >> Signed-off-by: Jane Chu <jane.chu@oracle.com> > Acked-by: Michal Hocko <mhocko@suse.com> > > 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.
Indeed, will make the above changes. Thanks for reviewing!
-jane
> > 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 >>
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