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gfs2: fix race between gfs2_freeze_func and unmount 

As part of the freeze operation, gfs2_freeze_func() is left blocking
on a request to hold the sd_freeze_gl in SH. This glock is held in EX
by the gfs2_freeze() code.

A subsequent call to gfs2_unfreeze() releases the EXclusively held
sd_freeze_gl, which allows gfs2_freeze_func() to acquire it in SH and
resume its operation.

gfs2_unfreeze(), however, doesn't wait for gfs2_freeze_func() to complete.
If a umount is issued right after unfreeze, it could result in an
inconsistent filesystem because some journal data (statfs update) isn't
written out.

Refer to commit 24972557b1 for a more detailed explanation of how
freeze/unfreeze work.

This patch causes gfs2_unfreeze() to wait for gfs2_freeze_func() to
complete before returning to the user.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Abhi Das 2019-04-30 16:53:47 -05:00 committed by Andreas Gruenbacher
parent fbb27873f2
commit 8f91821990
2 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/gfs2/incore.h
View File

@ -621,6 +621,7 @@ enum {
SDF_SKIP_DLM_UNLOCK = 8,
SDF_FORCE_AIL_FLUSH = 9,
SDF_AIL1_IO_ERROR = 10,
SDF_FS_FROZEN = 11,
};
enum gfs2_freeze_state {

8
fs/gfs2/super.c
View File

@ -973,8 +973,7 @@ void gfs2_freeze_func(struct work_struct *work)
if (error) {
printk(KERN_INFO "GFS2: couldn't get freeze lock : %d\n", error);
gfs2_assert_withdraw(sdp, 0);
}
else {
} else {
atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
error = thaw_super(sb);
if (error) {
@ -987,6 +986,8 @@ void gfs2_freeze_func(struct work_struct *work)
gfs2_glock_dq_uninit(&freeze_gh);
}
deactivate_super(sb);
clear_bit_unlock(SDF_FS_FROZEN, &sdp->sd_flags);
wake_up_bit(&sdp->sd_flags, SDF_FS_FROZEN);
return;
}
@ -1029,6 +1030,7 @@ static int gfs2_freeze(struct super_block *sb)
msleep(1000);
}
error = 0;
set_bit(SDF_FS_FROZEN, &sdp->sd_flags);
out:
mutex_unlock(&sdp->sd_freeze_mutex);
return error;
@ -1053,7 +1055,7 @@ static int gfs2_unfreeze(struct super_block *sb)
gfs2_glock_dq_uninit(&sdp->sd_freeze_gh);
mutex_unlock(&sdp->sd_freeze_mutex);
return 0;
return wait_on_bit(&sdp->sd_flags, SDF_FS_FROZEN, TASK_INTERRUPTIBLE);
}
/**