• Darrick J. Wong's avatar
    block: optionally snapshot page contents to provide stable pages during write · ffecfd1a
    Darrick J. Wong authored
    This provides a band-aid to provide stable page writes on jbd without
    needing to backport the fixed locking and page writeback bit handling
    schemes of jbd2.  The band-aid works by using bounce buffers to snapshot
    page contents instead of waiting.
    
    For those wondering about the ext3 bandage -- fixing the jbd locking
    (which was done as part of ext4dev years ago) is a lot of surgery, and
    setting PG_writeback on data pages when we actually hold the page lock
    dropped ext3 performance by nearly an order of magnitude.  If we're
    going to migrate iscsi and raid to use stable page writes, the
    complaints about high latency will likely return.  We might as well
    centralize their page snapshotting thing to one place.
    Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Tested-by: default avatarAndy Lutomirski <luto@amacapital.net>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Artem Bityutskiy <dedekind1@gmail.com>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Mark Fasheh <mfasheh@suse.com>
    Cc: Steven Whitehouse <swhiteho@redhat.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Eric Van Hensbergen <ericvh@gmail.com>
    Cc: Ron Minnich <rminnich@sandia.gov>
    Cc: Latchesar Ionkov <lucho@ionkov.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    ffecfd1a
super.c 83.6 KB