| Message ID | 534f275016296996f54ecf65168bb3392b6f653d.1591699601.git.riteshh@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCHv2,1/1] ext4: mballoc: Use this_cpu_read instead of this_cpu_ptr | expand |
On Tue, Jun 09, 2020 at 04:23:10PM +0530, Ritesh Harjani wrote: > Simplify reading a seq variable by directly using this_cpu_read API > instead of doing this_cpu_ptr and then dereferencing it. > > This also avoid the below kernel BUG: which happens when > CONFIG_DEBUG_PREEMPT is enabled I see this warning all the time with ext4 using tests VMs, so lets get this fixed ASAP before -rc1: Reviewed-by: Christoph Hellwig <hch@lst.de>
On 6/10/20 11:55 AM, Christoph Hellwig wrote: > On Tue, Jun 09, 2020 at 04:23:10PM +0530, Ritesh Harjani wrote: >> Simplify reading a seq variable by directly using this_cpu_read API >> instead of doing this_cpu_ptr and then dereferencing it. >> >> This also avoid the below kernel BUG: which happens when >> CONFIG_DEBUG_PREEMPT is enabled > > I see this warning all the time with ext4 using tests VMs, so lets get > this fixed ASAP before -rc1: Couldn't agree more. > > Reviewed-by: Christoph Hellwig <hch@lst.de> > Thanks -ritesh
On Tue, Jun 09, 2020 at 11:25:38PM -0700, Christoph Hellwig wrote: > On Tue, Jun 09, 2020 at 04:23:10PM +0530, Ritesh Harjani wrote: > > Simplify reading a seq variable by directly using this_cpu_read API > > instead of doing this_cpu_ptr and then dereferencing it. > > > > This also avoid the below kernel BUG: which happens when > > CONFIG_DEBUG_PREEMPT is enabled > > I see this warning all the time with ext4 using tests VMs, so lets get > this fixed ASAP before -rc1: > > Reviewed-by: Christoph Hellwig <hch@lst.de> Thanks, applied. - Ted
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index a9083113a8c0..c0a331e2feb0 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4708,7 +4708,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, } ac->ac_op = EXT4_MB_HISTORY_PREALLOC; - seq = *this_cpu_ptr(&discard_pa_seq); + seq = this_cpu_read(discard_pa_seq); if (!ext4_mb_use_preallocated(ac)) { ac->ac_op = EXT4_MB_HISTORY_ALLOC; ext4_mb_normalize_request(ac, ar);
Simplify reading a seq variable by directly using this_cpu_read API instead of doing this_cpu_ptr and then dereferencing it. This also avoid the below kernel BUG: which happens when CONFIG_DEBUG_PREEMPT is enabled 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 Fixes: 42f56b7a4a7d ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling") Suggested-by: Borislav Petkov <bp@alien8.de> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com> Reported-by: syzbot+82f324bb69744c5f6969@syzkaller.appspotmail.com --- fs/ext4/mballoc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)