On Mon, 2010-11-22 at 17:21 +0800, Li Zefan wrote: > > Have a look in fs/super.c:generic_shutdown_super(), called by > > fs/super.c:kill_anon_super(), where the super method ->put_super() is > > called, setting the super s_fs_info to NULL, before taking the sb_lock > > and removing it from the list of supers. > > > > Here's my patch. > > > > btrfs - fix race between btrfs_get_sb() and umount > > > > From: Ian Kent <raven@xxxxxxxxxx> > > > > When mounting a btrfs file system btrfs_test_super() may attempt to > > use sb->s_fs_info, the btrfs root, of a super block that is going away > > and that has had the btrfs root set to NULL in its ->put_super(). But > > if the super block is going away it cannot be an existing super block > > so we can return false in this case. > > I think your analysis is right. > > Actually I ran the test script (posted in an earlier email), and it > still crashed without your supplementary patch. And vice versa, as we found out working the Fedora bug, when I thought this was the actual bug at one point, both patches are needed. > > > > > Signed-off-by: Ian Kent <raven@xxxxxxxxxx> > > --- > > > > fs/btrfs/super.c | 6 ++++++ > > 1 files changed, 6 insertions(+), 0 deletions(-) > > > > > > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c > > index 6b57da3..960b320 100644 > > --- a/fs/btrfs/super.c > > +++ b/fs/btrfs/super.c > > @@ -565,6 +565,12 @@ static int btrfs_test_super(struct super_block *s, void *data) > > struct btrfs_fs_devices *test_fs_devices = data->fs_info->fs_devices; > > struct btrfs_root *root = btrfs_sb(s); > > > > + /* > > + * If this super block is going away, return false as it > > + * can't match as an existing super block. > > + */ > > + if (!atomic_read(&s->s_active)) > > + return 0; > > return root->fs_info->fs_devices == test_fs_devices; > > } > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
