Re: [RFC PATCH v2 1/9] block: add nr_mirrors to request_queue
From: Andreas Dilger <hidden>
Date: 2019-02-13 10:26:19
Also in:
linux-fsdevel, linux-xfs
On Feb 13, 2019, at 2:50 AM, Bob Liu [off-list ref] wrote:
When fs data/metadata checksum mismatch, lower block devices may have other correct copies. e.g if we did raid1 for protecting fs metadata. Then fs could try other copies of metadata instead of panic, but fs need be awared how many mirrors the block devices have. This patch add @nr_mirrors to struct request_queue which is similar as blk_queue_nonrot(), filesystem can grab device request queue and check the number of mirrors of this block device. @nr_mirrors is 1 by default which means only one copy, drivers e.g raid1 are responsible for setting the right value. The maximum value is BITS_PER_LONG which is 32 or 64. That should be big enough else retry lantency may be too high. Also added helper functions for get/set the number of mirrors for a specific device request queue. Todo: * Export nr_mirrors through /sysfs. Signed-off-by: Bob Liu <redacted>
quoted hunk ↗ jump to hunk
diff --git a/block/blk-settings.c b/block/blk-settings.c index 3e7038e475ee..38e4d7e675e6 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c@@ -844,6 +844,30 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua) +/* + * Set the number of read redundant mirrors. + */ +bool blk_queue_set_mirrors(struct request_queue *q, unsigned short mirrors) +{ + if(q->nr_mirrors >= BLKDEV_MAX_MIRRORS) { + printk("blk_queue_set_mirrors: %d exceed max mirrors(%d)\n", + mirrors, BLKDEV_MAX_MIRRORS);
Need to supply a KERN_ level here. Cheers, Andreas
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