Motivation: When fs data/metadata checksum mismatch, lower block devices may have other correct copies. e.g. If XFS successfully reads a metadata buffer off a raid1 but decides that the metadata is garbage, today it will shut down the entire filesystem without trying any of the other mirrors. This is a severe loss of service, and we propose these patches to have XFS try harder to avoid failure. This patch prototype this mirror retry idea by: * Adding @nr_mirrors to struct request_queue which is similar as blk_queue_nonrot(), filesystem can grab device request queue and check max mirrors this block device has. Helper functions were also added to get/set the nr_mirrors. * Expanding bi_write_hint to bi_rw_hint, now @bi_rw_hint has three meanings. 1.Original write_hint. 2.end_io() will update @bi_rw_hint to reflect which mirror this i/o really happened. 3.Fs set @bi_rw_hint to force driver e.g raid1 read from a specific mirror. * Modify md/raid1 to support this retry feature. * Add b_rw_hint to xfs_buf This patch adds a new field b_rw_hint to xfs_buf. We will use this to set the new bio->bi_rw_hint when submitting the read request, and also to store the returned mirror when the read compleates * Add device retry This patch add some logic to xfs_buf_read_map. If the read verify fails, we loop over the available mirrors and retry the read * Rewrite retried read When the read verification fails, but the retry succeedes write the buffer back to correct the bad mirror * Add tracepoints and logging to alternate device retry. This patch adds new log entries and trace points to the alternate device retry error path. We're not planning to take over all 16 bits of the read hint field; just looking for feedback about the sanity of the overall approach. Allison Henderson (4): xfs: Add b_rw_hint to xfs_buf xfs: Add device retry xfs: Rewrite retried read xfs: Add tracepoints and logging to alternate device retry Bob Liu (3): block: add nr_mirrors to request_queue block: expand write_hint of bio/request to rw_hint md: raid1: handle bi_rw_hint accordingly Documentation/block/biodoc.txt | 7 ++++++ block/bio.c | 2 +- block/blk-core.c | 13 ++++++++++- block/blk-merge.c | 8 +++---- block/blk-settings.c | 18 ++++++++++++++ block/bounce.c | 2 +- drivers/md/raid1.c | 33 ++++++++++++++++++++++---- drivers/md/raid5.c | 10 ++++---- drivers/md/raid5.h | 2 +- drivers/nvme/host/core.c | 2 +- fs/block_dev.c | 6 +++-- fs/btrfs/extent_io.c | 3 ++- fs/buffer.c | 3 ++- fs/direct-io.c | 3 ++- fs/ext4/page-io.c | 7 ++++-- fs/f2fs/data.c | 2 +- fs/iomap.c | 3 ++- fs/mpage.c | 2 +- fs/xfs/xfs_aops.c | 4 ++-- fs/xfs/xfs_buf.c | 53 ++++++++++++++++++++++++++++++++++++++++-- fs/xfs/xfs_buf.h | 8 +++++++ fs/xfs/xfs_trace.h | 6 ++++- include/linux/blk_types.h | 2 +- include/linux/blkdev.h | 5 +++- 24 files changed, 169 insertions(+), 35 deletions(-) -- 2.7.4
