• Darrick J. Wong's avatar
    xfs: manage inode DONTCACHE status at irele time · a03297a0
    Darrick J. Wong authored
    Right now, there are statements scattered all over the online fsck
    codebase about how we can't use XFS_IGET_DONTCACHE because of concerns
    about scrub's unusual practice of releasing inodes with transactions
    held.
    
    However, iget is the wrong place to handle this -- the DONTCACHE state
    doesn't matter at all until we try to *release* the inode, and here we
    get things wrong in multiple ways:
    
    First, if we /do/ have a transaction, we must NOT drop the inode,
    because the inode could have dirty pages, dropping the inode will
    trigger writeback, and writeback can trigger a nested transaction.
    
    Second, if the inode already had an active reference and the DONTCACHE
    flag set, the icache hit when scrub grabs another ref will not clear
    DONTCACHE.  This is sort of by design, since DONTCACHE is now used to
    initiate cache drops so that sysadmins can change a file's access mode
    between pagecache and DAX.
    
    Third, if we do actually have the last active reference to the inode, we
    can set DONTCACHE to avoid polluting the cache.  This is the /one/ case
    where we actually want that flag.
    
    Create an xchk_irele helper to encode all that logic and switch the
    online fsck code to use it.  Since this now means that nearly all
    scrubbers use the same xfs_iget flags, we can wrap them too.
    Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
    Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
    a03297a0
scrub.c 17.6 KB