On Sat, Mar 15, 2025 at 09:41:28PM -0400, Theodore Ts'o wrote: > On Fri, Mar 14, 2025 at 05:11:43PM +0530, Ojaswin Mujoo wrote: > > Currently, we access journal ino through sbi->s_es->s_journal_inum, > > which directly reads from the ext4 sb buffer head. If someone modifies > > this underneath us then the s_journal_inum field might get corrupted. > > > > Although direct block device modifications can be expected to cause > > issues in the FS, let's cache s_journal_inum in sbi->s_journal_ino so > > our checks can be more resillient. > > The reason why the block validity checks need to check against > s_journal_ino is to exempt the lookups done by ext4_journal_bmap() > from running afoul of the system zone checks, since the journal's data > blocks are considered part of the system zone. > > So this is something we need to do if the journal is actived, and if > it's active, then sbi->s_journal will be non-NULL, and so we can just > check to see if inode == sbi->s_journal instead. This will simplify I believe you mean inode == sbi->s_journal->j_inode here right? since that is enough to confirm if we are called via ext4_journal_bmap so we can avoid validity checks. Regards, ojaswin > the code, without needing to expand the ext4_sb_info structure. > > Cheers, > > - Ted
