Amir Goldstein <amir73il@xxxxxxxxx> writes: > On Mon, Sep 30, 2024 at 1:34 PM Jan Kara <jack@xxxxxxx> wrote: >> >> On Mon 30-09-24 12:15:11, Jan Stancek wrote: >> > On Mon, Aug 05, 2024 at 10:12:41PM +0200, Jan Kara wrote: >> > > When the filesystem is mounted with errors=remount-ro, we were setting >> > > SB_RDONLY flag to stop all filesystem modifications. We knew this misses >> > > proper locking (sb->s_umount) and does not go through proper filesystem >> > > remount procedure but it has been the way this worked since early ext2 >> > > days and it was good enough for catastrophic situation damage >> > > mitigation. Recently, syzbot has found a way (see link) to trigger >> > > warnings in filesystem freezing because the code got confused by >> > > SB_RDONLY changing under its hands. Since these days we set >> > > EXT4_FLAGS_SHUTDOWN on the superblock which is enough to stop all >> > > filesystem modifications, modifying SB_RDONLY shouldn't be needed. So >> > > stop doing that. >> > > >> > > Link: https://lore.kernel.org/all/000000000000b90a8e061e21d12f@xxxxxxxxxx >> > > Reported-by: Christian Brauner <brauner@xxxxxxxxxx> >> > > Signed-off-by: Jan Kara <jack@xxxxxxx> >> > > --- >> > > fs/ext4/super.c | 9 +++++---- >> > > 1 file changed, 5 insertions(+), 4 deletions(-) >> > > >> > > Note that this patch introduces fstests failure with generic/459 test because >> > > it assumes that either freezing succeeds or 'ro' is among mount options. But >> > > we fail the freeze with EFSCORRUPTED. This needs fixing in the test but at this >> > > point I'm not sure how exactly. >> > > >> > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c >> > > index e72145c4ae5a..93c016b186c0 100644 >> > > --- a/fs/ext4/super.c >> > > +++ b/fs/ext4/super.c >> > > @@ -735,11 +735,12 @@ static void ext4_handle_error(struct super_block *sb, bool force_ro, int error, >> > > >> > > ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only"); >> > > /* >> > > - * Make sure updated value of ->s_mount_flags will be visible before >> > > - * ->s_flags update >> > > + * EXT4_FLAGS_SHUTDOWN was set which stops all filesystem >> > > + * modifications. We don't set SB_RDONLY because that requires >> > > + * sb->s_umount semaphore and setting it without proper remount >> > > + * procedure is confusing code such as freeze_super() leading to >> > > + * deadlocks and other problems. >> > > */ >> > > - smp_wmb(); >> > > - sb->s_flags |= SB_RDONLY; >> > >> > Hi, >> > >> > shouldn't the SB_RDONLY still be set (in __ext4_remount()) for the case >> > when user triggers the abort with mount(.., "abort")? Because now we seem >> > to always hit the condition that returns EROFS to user-space. >> >> Thanks for report! I agree returning EROFS from the mount although >> 'aborting' succeeded is confusing and is mostly an unintended side effect >> that after aborting the fs further changes to mount state are forbidden but >> the testcase additionally wants to remount the fs read-only. > > Regardless of what is right or wrong to do in ext4, I don't think that the test > really cares about remount read-only. > I don't see anything in the test that requires it. Gabriel? > If I remove MS_RDONLY from the test it works just fine. If I recall correctly, no, there is no need for the MS_RDONLY. We only care about getting the event to test FS_ERROR. Thanks, > > Any objection for LTP maintainers to apply this simple test fix? > > Thanks, > Amir. > > --- a/testcases/kernel/syscalls/fanotify/fanotify22.c > +++ b/testcases/kernel/syscalls/fanotify/fanotify22.c > @@ -57,7 +57,7 @@ static struct fanotify_fid_t bad_link_fid; > static void trigger_fs_abort(void) > { > SAFE_MOUNT(tst_device->dev, MOUNT_PATH, tst_device->fs_type, > - MS_REMOUNT|MS_RDONLY, "abort"); > + MS_REMOUNT, "abort"); > } -- Gabriel Krisman Bertazi
