| Message ID | 5823da614460b8c40809e6e0a6de172a9c4f4611.1468965479.git.cggong@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 2016-07-20 16:11:16, Charles Gong wrote: > "SYSRQ + J" triggers a call to emergency_thaw_all(). Currently, this > is an infinite loop. Once we trigger it, we'll need to do a hard > power-cycle. There are users reporting this bug from 2012 to 2016, for > example, at https://bugzilla.kernel.org/show_bug.cgi?id=47741. > > This happens because thaw_bdev() fails to return -EINVAL in the > non-frozen case, so fix it so that do_one_thaw() can recognize this case > and quit from looping. I checked that none of the other thaw_bdev() > callers check the return value. > > The regression was introduced in commit 4504230a7156 ("freeze_bdev: grab > active reference to frozen superblocks"). > > Reviewed-by: Chris Mason <clm@fb.com> > Signed-off-by: Charles Gong <cggong@fb.com> Acked-by: Pavel Machek <pavel@ucw.cz> (even magic should be finite...)
diff --git a/fs/block_dev.c b/fs/block_dev.c index 71ccab1..14f015e 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -301,14 +301,12 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb) error = sb->s_op->thaw_super(sb); else error = thaw_super(sb); - if (error) { + if (error) bdev->bd_fsfreeze_count++; - mutex_unlock(&bdev->bd_fsfreeze_mutex); - return error; - } + out: mutex_unlock(&bdev->bd_fsfreeze_mutex); - return 0; + return error; } EXPORT_SYMBOL(thaw_bdev);
"SYSRQ + J" triggers a call to emergency_thaw_all(). Currently, this is an infinite loop. Once we trigger it, we'll need to do a hard power-cycle. There are users reporting this bug from 2012 to 2016, for example, at https://bugzilla.kernel.org/show_bug.cgi?id=47741. This happens because thaw_bdev() fails to return -EINVAL in the non-frozen case, so fix it so that do_one_thaw() can recognize this case and quit from looping. I checked that none of the other thaw_bdev() callers check the return value. The regression was introduced in commit 4504230a7156 ("freeze_bdev: grab active reference to frozen superblocks"). Reviewed-by: Chris Mason <clm@fb.com> Signed-off-by: Charles Gong <cggong@fb.com> --- fs/block_dev.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)