Does unmount() sync dirty buffers

Does unmount() sync dirty buffers

[Ravishankar]

Hello,

When we unmount a file system with the umount command or the umount()
system call, does the kernel sync the dirty buffers before the file system
is unmounted?I am assuming that the file system is not 'busy' (i.e no open
files etc) and no force options are specified. When I did a walk-through of
do_umount() call in fs/namespace.c, I could not find calls to sync any
dirty pages that might exist.

Thanks!
Ravi
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Does unmount() sync dirty buffers

[Mulyadi Santosa]

Hi :)

On Tue, Feb 14, 2012 at 21:13, Ravishankar <cyberax82@gmail.com> wrote:
> Hello,
>
> When we unmount a file system with the umount command or the umount() system
> call, does the kernel sync the dirty buffers before the file system is
> unmounted?

Yep, it flushes them.  But i forget the exact code path, since last
time I checked it, it was in 2.4.x

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

Does unmount() sync dirty buffers

[Manish Katiyar]

[Apparently I forgot to cc list]

On Tue, Feb 14, 2012 at 10:04 PM, Manish Katiyar <mkatiyar@gmail.com> wrote:
> On Tue, Feb 14, 2012 at 7:43 PM, Ravishankar <cyberax82@gmail.com> wrote:
>> Hello,
>>
>> When we unmount a file system with the umount command or the umount() system
>> call, does the kernel sync the dirty buffers before the file system is
>> unmounted?I am assuming that the file system is not 'busy' (i.e no open
>> files etc) and no force options are specified. When I did a walk-through of
>> do_umount() call in fs/namespace.c, I could not find calls to sync any dirty
>> pages that might exist.
>
> yes, most of the filesystem have their own function to sync fs. Look
> for the function pointer "sync_fs"
>
> For eg..for ext4
>
> generic_shutdown_super -> sync_filesystem -> __sync_filesystem ->
> sync_fs -> ext4_sync_fs
> --
> Thanks -
> Manish



-- 
Thanks -
Manish

Does unmount() sync dirty buffers

[Ravishankar]

On Wed, Feb 15, 2012 at 2:08 PM, Manish Katiyar <mkatiyar@gmail.com> wrote:

> [Apparently I forgot to cc list]
>
> On Tue, Feb 14, 2012 at 10:04 PM, Manish Katiyar <mkatiyar@gmail.com>
> wrote:
> > On Tue, Feb 14, 2012 at 7:43 PM, Ravishankar <cyberax82@gmail.com>
> wrote:
> >> Hello,
> >>
> >> When we unmount a file system with the umount command or the umount()
> system
> >> call, does the kernel sync the dirty buffers before the file system is
> >> unmounted?I am assuming that the file system is not 'busy' (i.e no open
> >> files etc) and no force options are specified. When I did a
> walk-through of
> >> do_umount() call in fs/namespace.c, I could not find calls to sync any
> dirty
> >> pages that might exist.
> >
> > yes, most of the filesystem have their own function to sync fs. Look
> > for the function pointer "sync_fs"
> >
> > For eg..for ext4
> >
> > generic_shutdown_super -> sync_filesystem -> __sync_filesystem ->
> > sync_fs -> ext4_sync_fs
> > --
> > Thanks -
> > Manish
>
>
>
> --
> Thanks -
> Manish
>

Thanks a lot.Just to add,  generic_shutdown_super() is called thus:

umount systemcall
-->mntput_no_expire()-->__mntput()-->deactivate_super()-->deactivate_locked_super()-->kill_block_super()-->generic_shutdown_super()
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