On 2018/07/18 17:58, syzbot wrote: > mmap: syz-executor7 (10902) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst. There are many reports which are stalling inside __getblk_gfp(). And there is horrible comment for __getblk_gfp(): /* * __getblk_gfp() will locate (and, if necessary, create) the buffer_head * which corresponds to the passed block_device, block and size. The * returned buffer has its reference count incremented. * * __getblk_gfp() will lock up the machine if grow_dev_page's * try_to_free_buffers() attempt is failing. FIXME, perhaps? */ This report is stalling after mount() completed and process used remap_file_pages(). I think that we might need to use debug printk(). But I don't know what to examine. > CPU: 1 PID: 10863 Comm: syz-executor0 Not tainted 4.18.0-rc5+ #151 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x50 kernel/kcov.c:106 > Code: e2 00 01 1f 00 48 8b 75 08 75 2b 8b 90 90 12 00 00 83 fa 02 75 20 48 8b 88 98 12 00 00 8b 80 94 12 00 00 48 8b 11 48 83 c2 01 <48> 39 d0 76 07 48 89 34 d1 48 89 11 5d c3 0f 1f 00 55 40 0f b6 d6 > RSP: 0018:ffff8801913be760 EFLAGS: 00000216 > RAX: 0000000000040000 RBX: ffff88018e06b348 RCX: ffffc90001e34000 > RDX: 0000000000040000 RSI: ffffffff81d44df2 RDI: 0000000000000007 > RBP: ffff8801913be760 R08: ffff8801b465c540 R09: ffffed003b5e46d6 > R10: 0000000000000003 R11: 0000000000000006 R12: dffffc0000000000 > R13: 0000000000000042 R14: 0000000000000001 R15: 0000000000000020 > FS: 00007f53ece9c700(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000119f218 CR3: 00000001ba743000 CR4: 00000000001406e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > init_page_buffers+0x3e2/0x530 fs/buffer.c:904 > grow_dev_page fs/buffer.c:947 [inline] > grow_buffers fs/buffer.c:1009 [inline] > __getblk_slow fs/buffer.c:1036 [inline] > __getblk_gfp+0x906/0xb10 fs/buffer.c:1313 > __bread_gfp+0x2d/0x310 fs/buffer.c:1347 > sb_bread include/linux/buffer_head.h:307 [inline] > fat12_ent_bread+0x14e/0x3d0 fs/fat/fatent.c:75 > fat_ent_read_block fs/fat/fatent.c:441 [inline] > fat_alloc_clusters+0x8ce/0x16e0 fs/fat/fatent.c:489 > fat_add_cluster+0x7a/0x150 fs/fat/inode.c:101 > __fat_get_block fs/fat/inode.c:148 [inline] > fat_get_block+0x375/0xaf0 fs/fat/inode.c:183 > __block_write_begin_int+0x50d/0x1b00 fs/buffer.c:1958 > __block_write_begin fs/buffer.c:2008 [inline] > block_write_begin+0xda/0x370 fs/buffer.c:2067 > cont_write_begin+0x569/0x860 fs/buffer.c:2417 > fat_write_begin+0x8d/0x120 fs/fat/inode.c:229 > generic_perform_write+0x3ae/0x6c0 mm/filemap.c:3139 > __generic_file_write_iter+0x26e/0x630 mm/filemap.c:3264 > generic_file_write_iter+0x438/0x870 mm/filemap.c:3292 > call_write_iter include/linux/fs.h:1793 [inline] > new_sync_write fs/read_write.c:474 [inline] > __vfs_write+0x6c6/0x9f0 fs/read_write.c:487 > __kernel_write+0x10c/0x380 fs/read_write.c:506 > do_acct_process+0x1148/0x1660 kernel/acct.c:520 > acct_pin_kill+0x2e/0x100 kernel/acct.c:174 > pin_kill+0x29f/0xb60 fs/fs_pin.c:50 > acct_on+0x63b/0x8b0 kernel/acct.c:254 > __do_sys_acct kernel/acct.c:286 [inline] > __se_sys_acct kernel/acct.c:273 [inline] > __x64_sys_acct+0xc2/0x1f0 kernel/acct.c:273 > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe
