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Date: Fri, 12 Jun 2020 19:09:04 +0530 From: Ritesh Harjani <riteshh@...ux.ibm.com> To: Ido Schimmel <idosch@...sch.org> Cc: syzbot <syzbot+82f324bb69744c5f6969@...kaller.appspotmail.com>, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, linux-next@...r.kernel.org, sfr@...b.auug.org.au, syzkaller-bugs@...glegroups.com, tytso@....edu Subject: Re: linux-next test error: BUG: using smp_processor_id() in preemptible [ADDR] code: syz-fuzzer/6792 On 6/12/20 6:13 PM, Ido Schimmel wrote: > On Tue, Jun 02, 2020 at 06:11:29PM +0530, Ritesh Harjani wrote: >> #syz test: >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git >> 0e21d4620dd047da7952f44a2e1ac777ded2d57e > >> >From cc1cf67d99d5fa61db0651c89c288df31bad6b8e Mon Sep 17 00:00:00 2001 >> From: Ritesh Harjani <riteshh@...ux.ibm.com> >> Date: Tue, 2 Jun 2020 17:54:12 +0530 >> Subject: [PATCH 1/1] ext4: mballoc: Use raw_cpu_ptr in case if preemption is enabled >> >> It doesn't matter really in ext4_mb_new_blocks() about whether the code >> is rescheduled on any other cpu due to preemption. Because we care >> about discard_pa_seq only when the block allocation fails and then too >> we add the seq counter of all the cpus against the initial sampled one >> to check if anyone has freed any blocks while we were doing allocation. >> >> So just use raw_cpu_ptr to not trigger this BUG. >> >> BUG: using smp_processor_id() in preemptible [00000000] code: syz-fuzzer/6927 >> caller is ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711 >> CPU: 1 PID: 6927 Comm: syz-fuzzer Not tainted 5.7.0-next-20200602-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:77 [inline] >> dump_stack+0x18f/0x20d lib/dump_stack.c:118 >> check_preemption_disabled+0x20d/0x220 lib/smp_processor_id.c:48 >> ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711 >> ext4_ext_map_blocks+0x201b/0x33e0 fs/ext4/extents.c:4244 >> ext4_map_blocks+0x4cb/0x1640 fs/ext4/inode.c:626 >> ext4_getblk+0xad/0x520 fs/ext4/inode.c:833 >> ext4_bread+0x7c/0x380 fs/ext4/inode.c:883 >> ext4_append+0x153/0x360 fs/ext4/namei.c:67 >> ext4_init_new_dir fs/ext4/namei.c:2757 [inline] >> ext4_mkdir+0x5e0/0xdf0 fs/ext4/namei.c:2802 >> vfs_mkdir+0x419/0x690 fs/namei.c:3632 >> do_mkdirat+0x21e/0x280 fs/namei.c:3655 >> do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> >> Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com> >> Reported-by: syzbot+82f324bb69744c5f6969@...kaller.appspotmail.com > > Hi, > > Are you going to submit this patch formally? Without it I'm constantly > seeing the above splat. > I see Ted has already taken v2 of this patch in his dev repo. Should be able to see in linux tree soon. https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=811985365378df01386c3cfb7ff716e74ca376d5 -ritesh
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