Messages in this thread | | | Date | Tue, 14 Jun 2022 17:40:39 +0100 | Subject | Re: [PATCH] writeback: Avoid grabbing the wb if the we don't add it to dirty list | From | Suzuki K Poulose <> |
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On 14/06/2022 15:29, Jan Kara wrote: > On Tue 14-06-22 13:46:18, Suzuki K Poulose wrote: >> Commit 10e14073107d moved grabbing the wb for an inode early enough, >> skipping the checks whether if this inode needs to be really added >> to the dirty list (backed by blockdev or unhashed inode). This causes >> a crash with kdevtmpfs as below, on an arm64 Juno board, as below: >> >> [ 1.446493] printk: console [ttyAMA0] printing thread started >> [ 1.447195] printk: bootconsole [pl11] printing thread stopped >> [ 1.467193] Unable to handle kernel paging request at virtual address ffff800871242000 >> [ 1.467793] Mem abort info: >> [ 1.468093] ESR = 0x0000000096000005 >> [ 1.468413] EC = 0x25: DABT (current EL), IL = 32 bits >> [ 1.468741] SET = 0, FnV = 0 >> [ 1.469093] EA = 0, S1PTW = 0 >> [ 1.469396] FSC = 0x05: level 1 translation fault >> [ 1.470493] Data abort info: >> [ 1.470793] ISV = 0, ISS = 0x00000005 >> [ 1.471093] CM = 0, WnR = 0 >> [ 1.471444] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000081c10000 >> [ 1.471798] [ffff800871242000] pgd=10000008fffff003, >> p4d=10000008fffff003, pud=0000000000000000 >> [ 1.472836] Internal error: Oops: 96000005 [#1] PREEMPT SMP >> [ 1.472918] Modules linked in: >> [ 1.473085] CPU: 1 PID: 35 Comm: kdevtmpfs Tainted: G T 5.19.0-rc1+ #49 >> [ 1.473246] Hardware name: Foundation-v8A (DT) >> [ 1.473345] pstate: 40400009 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> [ 1.473493] pc : locked_inode_to_wb_and_lock_list+0xbc/0x2a4 >> [ 1.473656] lr : locked_inode_to_wb_and_lock_list+0x8c/0x2a4 >> [ 1.473820] sp : ffff80000b77bc10 >> [ 1.473901] x29: ffff80000b77bc10 x28: 0000000000000001 x27: 0000000000000004 >> [ 1.474193] x26: 0000000000000000 x25: ffff000800888600 x24: ffff0008008885e8 >> [ 1.474393] x23: ffff80000848ddd4 x22: ffff80000a754f30 x21: ffff80000a7eaaf0 >> [ 1.474693] x20: ffff000800888150 x19: ffff80000b6a4150 x18: ffff80000ac3ac00 >> [ 1.474917] x17: 0000000070526bee x16: 000000003ac581ee x15: ffff80000ac42660 >> [ 1.475195] x14: 0000000000000000 x13: 0000000000007a60 x12: 0000000000000002 >> [ 1.475428] x11: ffff80000a7eaaf0 x10: 0000000000000004 x9 : 000000008845fe88 >> [ 1.475622] x8 : ffff000800868000 x7 : ffff80000ab98000 x6 : 00000000114514e2 >> [ 1.475893] x5 : 0000000000000000 x4 : 0000000000020019 x3 : 0000000000000001 >> [ 1.476113] x2 : ffff800871242000 x1 : ffff800871242000 x0 : ffff000800868000 >> [ 1.476393] Call trace: >> [ 1.476493] locked_inode_to_wb_and_lock_list+0xbc/0x2a4 >> [ 1.476605] __mark_inode_dirty+0x3d8/0x6e0 >> [ 1.476793] simple_setattr+0x5c/0x84 >> [ 1.476933] notify_change+0x3ec/0x470 >> [ 1.477096] handle_create+0x1b8/0x224 >> [ 1.477193] devtmpfsd+0x98/0xf8 >> [ 1.477342] kthread+0x124/0x130 >> [ 1.477512] ret_from_fork+0x10/0x20 >> [ 1.477670] Code: b9000802 d2800023 d53cd042 8b020021 (f823003f) >> [ 1.477793] ---[ end trace 0000000000000000 ]--- >> [ 1.478093] note: kdevtmpfs[35] exited with preempt_count 2 >> >> The problem was bisected to the above commit and moving the bail check >> early solves the problem for me. >> >> Fixes: 10e14073107d ("writeback: Fix inode->i_io_list not be protected by inode->i_lock error") >> CC: stable@vger.kernel.org >> Cc: Jchao Sun <sunjunchao2870@gmail.com> >> Cc: Jan Kara <jack@suse.cz> >> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> > > Thanks for debugging this! The problem actually is not that we cannot call > locked_inode_to_wb_and_lock_list() for devtmpfs inode. The problem is that > we get called so early during boot that noop_backing_dev_info is not > initialized yet and that breaks the code. But I agree the quick fix for > this breakage is to exclude unhashed inodes early in __mark_inode_dirty(). > I'll update the changelog and code comment (and cleanup the condition when > moving it) and push the result to my tree.
Thanks for the clarification. Btw, here is another report, that is fixed with the same patch [0].
[0] https://lore.kernel.org/linux-arm-kernel/YqiJH1phG%2FLWu9bs@monolith.localdoman/
Suzuki
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