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SubjectRe: [PATCH v2] f2fs: Fix deadlock in shutdown ioctl
On 05/17, Chao Yu wrote:
> On 2018/5/17 16:03, Sahitya Tummala wrote:
> > f2fs_ioc_shutdown() ioctl gets stuck in the below path
> > when issued with F2FS_GOING_DOWN_FULLSYNC option.
> >
> > __switch_to+0x90/0xc4
> > percpu_down_write+0x8c/0xc0
> > freeze_super+0xec/0x1e4
> > freeze_bdev+0xc4/0xcc
> > f2fs_ioctl+0xc0c/0x1ce0
> > f2fs_compat_ioctl+0x98/0x1f0
> >
> > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> > ---
> > v2:
> > remove lock coverage for only F2FS_GOING_DOWN_FULLSYNC case as suggested by Chao.
> >
> > fs/f2fs/file.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 6b94f19..5a132c9 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -1857,6 +1857,7 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
>
> How about:
>
> if (in != F2FS_GOING_DOWN_FULLSYNC)
> mnt_want_write_file();
>
> switch()
> {
> handle command;
> }
>
> if (in != F2FS_GOING_DOWN_FULLSYNC)
> mnt_drop_write_file();
>
> Thanks,

if (in == F2FS_GOING_DOWN_FULLSYNC) {
sb = freeze_bdev();
if (IS_ERR(sb))
return PTR_ERR(sb);
if (unlikely(!sb))
return -EINVAL;
}

ret = mnt_want_write_file();
...
switch() {
case F2FS_GOING_DOWN_FULLSYNC:
f2fs_stop_checkpoint();
dhaw_bdev();
break;
...
}

drop:
...


>
> >
> > switch (in) {
> > case F2FS_GOING_DOWN_FULLSYNC:
> > + mnt_drop_write_file(filp);
> > sb = freeze_bdev(sb->s_bdev);
> > if (IS_ERR(sb)) {
> > ret = PTR_ERR(sb);
> > @@ -1894,7 +1895,8 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
> >
> > f2fs_update_time(sbi, REQ_TIME);
> > out:
> > - mnt_drop_write_file(filp);
> > + if (in != F2FS_GOING_DOWN_FULLSYNC)
> > + mnt_drop_write_file(filp);
> > return ret;
> > }
> >
> >

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