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SubjectRe: Mount -o sync regression in 2.6.31
On Fri, 13 Nov 2009 15:07:19 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 13 Nov 2009 14:47:27 -0800
> Stephen Hemminger <shemminger@vyatta.com> wrote:
>
> > Okay the scenario is:
> > 1. Mount floppy with ext2 filesystem in sync mode
> > 2. Write to floppy
> > 3. Prematurely eject floppy
> > 4. Unmount floppy
>
> I assume that by "prematurely eject", you mean that you waited until
> the activity LED had turned off, then hit the button without typing
> umount?

yes. no activity, but not unmounted

>
> Really, I think ext2 is just wrong here. At unmount time it runs
> ext2_sync_super(), which updates a few fields in the superblock and
> tries to write them back.
>
> But if the fs was mounted with `-osync' then the driver should be
> operating synchronously, dammit! That means that any time any syscall
> alters the filesystem's s_free_blocks_count, s_free_inodes_count or
> s_wtime, the driver should write those fields back to the superblock
> prior to returning from the syscall.

Agreed, but it looks like it has always done that.

> However that might be unreasonaly anal of us, because those fields
> aren't terribly important. A fsck will whine and fix them up.
>
> > This triggers this warning in 2.6.31 which did not occur in 2.6.30
>
> hm, I wonder why that changed. The warning's been there for a while.
>
> > [ 580.325447] floppy0: disk absent or changed during operation
> > [ 580.325454] lost page write due to I/O error on fd0
> > [ 580.958434] ------------[ cut here ]------------
> > [ 580.958437] WARNING: at fs/buffer.c:1152 mark_buffer_dirty+0x23/0x7d()
> > [ 580.958440] Hardware name: System Product Name
> > [ 580.958442] Modules linked in: hid_belkin binfmt_misc bridge stp llc kvm_intel kvm ipv6 video output pci_slot acpi_cpufreq cpufreq_powersave cpufreq_ondemand cpufreq_conservative cpufreq_userspace psmouse pcspkr serio_raw rtc_cmos wmi evdev sg sr_mod cdrom usbhid mvsas pata_acpi pata_marvell ata_piix libsas ahci igb sky2 scsi_transport_sas dca e1000e floppy dm_mirror dm_region_hash dm_log dm_snapshot dm_mod fuse
> > [ 580.958475] Pid: 8340, comm: umount Not tainted 2.6.30-rc6-bisect #12
> > [ 580.958477] Call Trace:
> > [ 580.958483] [<ffffffff80232ebb>] ? warn_slowpath_fmt+0xd9/0x10b
> > [ 580.958489] [<ffffffff80270031>] ? find_get_pages_tag+0x41/0xdd
> > [ 580.958494] [<ffffffff802782f0>] ? pagevec_lookup+0x17/0x1e
> > [ 580.958498] [<ffffffff80279377>] ? truncate_inode_pages_range+0x21d/0x31d
> > [ 580.958502] [<ffffffff80270db5>] ? wait_on_page_writeback_range+0xce/0x11b
> > [ 580.958507] [<ffffffff80245037>] ? bit_waitqueue+0x10/0xa0
> > [ 580.958510] [<ffffffff802be80d>] ? mark_buffer_dirty+0x23/0x7d
> > [ 580.958515] [<ffffffff803003eb>] ? ext2_sync_super+0x39/0x55
> > [ 580.958519] [<ffffffff8030079c>] ? ext2_put_super+0x34/0xc7
> > [ 580.958524] [<ffffffff802a3174>] ? generic_shutdown_super+0x70/0xfd
> > [ 580.958533] [<ffffffff802a3223>] ? kill_block_super+0x22/0x3a
> > [ 580.958537] [<ffffffff802a3831>] ? deactivate_super+0x43/0x5a
> > [ 580.958541] [<ffffffff802b56f9>] ? sys_umount+0x2d8/0x307
> > [ 580.958546] [<ffffffff8020aeeb>] ? system_call_fastpath+0x16/0x1b
> > [ 580.958549] ---[ end trace ccbde6411acd243f ]---
> > [ 580.958580] floppy0: disk absent or changed during operation
> > [ 580.958587] lost page write due to I/O error on fd0
>
> void mark_buffer_dirty(struct buffer_head *bh)
> {
> WARN_ON_ONCE(!buffer_uptodate(bh));
>
> that's expected, I expect. And it's just a WARN_ON_ONCE() so it
> won't be flooding logs. We could just delete it I suppose.
>
> > Bisecting between 2.6.30 and 2.6.31-rc1 reduced it down to:
> >
> > 8f184f27300f66f6dcc8296c2dae7a1fbe8429c9 is first bad commit
> > commit 8f184f27300f66f6dcc8296c2dae7a1fbe8429c9
> > Author: Frederic Weisbecker <fweisbec@gmail.com>
> > Date: Sat May 16 06:24:36 2009 +0200
> >
> > tracing/stat: replace linked list by an rbtree for sorting
>
> Current score:
>
> git: 4,559
> kernel developers: 0


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