On Sun 22-04-18 09:12:10, Amir Goldstein wrote: > If fs is frozen after mount and before the first file open, the > update of s_last_mounted bypasses freeze protection and prints out > a WARNING splat: > > $ mount /vdf > $ fsfreeze -f /vdf > $ cat /vdf/foo > > [ 31.578555] WARNING: CPU: 1 PID: 1415 at > fs/ext4/ext4_jbd2.c:53 ext4_journal_check_start+0x48/0x82 > > [ 31.614016] Call Trace: > [ 31.614997] __ext4_journal_start_sb+0xe4/0x1a4 > [ 31.616771] ? ext4_file_open+0xb6/0x189 > [ 31.618094] ext4_file_open+0xb6/0x189 > > This fix might not be free of open vs. freeze race, but it closes > a big hole. > > [backport hint: to apply to stable tree, just need to repace > sb_rdonly(sb) with (sb->s_flags & MS_RDONLY)] > Thanks for the patch. But a proper (race-free) fix for this is to use sb_start_intwrite(), before starting a handle and sb_end_intwrite() after stopping it. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
