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 <[email protected]> Signed-off-by: Jane Chu <[email protected]>Acked-by: Michal Hocko <[email protected]> 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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