Dave Chinner <david@xxxxxxxxxxxxx> writes: > On Wed, Feb 27, 2013 at 01:04:14AM +0000, Alasdair G Kergon wrote: >> (Quick pointers that might be relevant) >> >> EAGAIN, I'm not aware of dm itself returning that on the i/o path. > > Neither am I, but it's coming from somewhere in the IO path... Well, I don't really know anything about this topic, so I may be completely off the mark, but dm-raid1.c:mirror_map() does indeed return EWOULDBLOCK, and EWOULDBLOCK is #define'd to be EAGAIN, so it seems to me that dm-raid1 does indeed return EAGAIN for "rw == READA" (which I assume is read-ahead) if the "region is not in-sync": /* * If region is not in-sync queue the bio. */ if (!r || (r == -EWOULDBLOCK)) { if (rw == READA) return -EWOULDBLOCK; queue_bio(ms, bio, rw); return DM_MAPIO_SUBMITTED; } Regards, MF -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel