On 3/22/23 12:25 AM, Peter Xu wrote: > Hi, Muhammad, > > On Tue, Mar 21, 2023 at 05:21:15PM +0500, Muhammad Usama Anjum wrote: >> Thank you so much for the patch. I've tested hugetlb mem. This patch is >> working fine for hugetlb shmem: >> *shmid = shmget(2, size, SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W); >> mem = shmat(*shmid, 0, 0); >> >> I've found slight issue with hugetlb mem which has been mmaped: >> mem = mmap(NULL, size, PROT_READ | PROT_WRITE, >> MAP_ANONYMOUS | MAP_HUGETLB | MAP_PRIVATE, -1, 0); >> The issue is that even after witting to this memory, the wp flag is still >> present there and memory doesn't appear to be dirty when it should have >> been dirty. The temporary fix is to write to memory and write protect the >> memory one extra time. > > I looked into this today and found it's an existing bug that can trigger > with sync mode too.. as long as protection applied to unpopulated hugetlb > private mappings, then write to it. > > I've sent a fix for it here and have you copied: > > https://lore.kernel.org/linux-mm/20230321191840.1897940-1-peterx@xxxxxxxxxx/T/#u > > Please have a look and see whether it also fixes your issue. Thanks for sending the patch. I've replied on the sent patch. > > PS: recently I added a warning in commit c2da319c2e2789 and that can indeed > capture this one when verifying using pagemap. I'd guess your dmesg should > also contain something dumped. I didn't had debug_vm config enabled. I've enabled it now. I'm getting only the following stack trace in failure scenario: ok 1 Hugetlb shmem testing: all new pages must not be written (dirty) 0 ok 2 Hugetlb shmem testing: all pages must be written (dirty) 1 512 0 512 ok 3 Hugetlb mem testing: all new pages must not be written (dirty) 0 [ 10.086540] ------------[ cut here ]------------ [ 10.087758] WARNING: CPU: 0 PID: 175 at arch/x86/include/asm/pgtable.h:313 pagemap_scan_hugetlb_entry+0x19c/0x230 [ 10.090208] Modules linked in: [ 10.091059] CPU: 0 PID: 175 Comm: pagemap_ioctl Not tainted 6.3.0-rc3-next-20230320-00010-gdc395ccf1882 #88 [ 10.093224] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-5 04/01/2014 [ 10.095879] RIP: 0010:pagemap_scan_hugetlb_entry+0x19c/0x230 [ 10.097497] Code: 89 ca 41 89 c2 29 c8 4c 01 c2 49 39 d2 41 0f 43 c0 e9 53 ff ff ff 48 83 e2 9f 89 c7 31 ed 49 89 d1 83 e7 02 0f 84 30 ff ff ff <0f> 0b 31 ff e9 27 ff ff ff 48 83 e2 9f 44 89 c0 bf 01 00 00 00 bd [ 10.102528] RSP: 0018:ffffb6cd80303d10 EFLAGS: 00010202 [ 10.104002] RAX: 8000000000000ce7 RBX: 00007fcc84000000 RCX: 0000000000200000 [ 10.105989] RDX: 80000002f7c00c87 RSI: 0000000000000001 RDI: 0000000000000002 [ 10.108043] RBP: 0000000000000000 R08: 0000000000000200 R09: 80000002f7c00c87 [ 10.110004] R10: ffffa08541e3220c R11: 0000000000000000 R12: ffffa08541562420 [ 10.112335] R13: ffffb6cd80303e70 R14: 00007fcc84000000 R15: ffffffff8eae1520 [ 10.114688] FS: 00007fcc8454b740(0000) GS:ffffa0886fc00000(0000) knlGS:0000000000000000 [ 10.116960] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 10.118187] CR2: 00007fcc84000000 CR3: 0000000102838000 CR4: 0000000000750ef0 [ 10.119628] PKRU: 55555554 [ 10.120184] Call Trace: [ 10.120730] <TASK> [ 10.121206] __walk_page_range+0xbe/0x1b0 [ 10.122048] walk_page_range+0x15f/0x1a0 [ 10.122869] do_pagemap_cmd+0x239/0x390 [ 10.123672] __x64_sys_ioctl+0x8b/0xc0 [ 10.124462] do_syscall_64+0x3a/0x90 [ 10.125227] entry_SYSCALL_64_after_hwframe+0x72/0xdc [ 10.126326] RIP: 0033:0x7fcc8464bbab [ 10.127066] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00 [ 10.130868] RSP: 002b:00007fff9b864240 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 10.132412] RAX: ffffffffffffffda RBX: 0000000000001000 RCX: 00007fcc8464bbab [ 10.133880] RDX: 00007fff9b8642c0 RSI: 00000000c0586610 RDI: 0000000000000003 [ 10.135328] RBP: 00007fff9b864320 R08: 0000000000000001 R09: 0000000000000000 [ 10.136790] R10: 00007fff9b864217 R11: 0000000000000246 R12: 0000000000000000 [ 10.138285] R13: 00007fff9b8644f8 R14: 0000000000409df0 R15: 00007fcc84862020 [ 10.139729] </TASK> [ 10.140197] ---[ end trace 0000000000000000 ]--- not ok 4 Hugetlb mem testing: all pages must be written (dirty) 0 -2072900416 0 512 > > Thanks, > -- BR, Muhammad Usama Anjum
