On 03/08/2017 02:34 AM, Umesh Patel wrote: > Hello, > > We are registering BIO size of our storage device through linux kernel > API blk_queue_max_hw_sectors worth of 104K. So max size of BIO that > our block device can handle is 104 KB but kernel block layer is > sending 256 KB worth of BIO which is more than we are supporting. > This issue we are observing in 4.4 and also in latest 4.10.1 kernel > release. Until this we had not seen this issue. > > From the kernel source code history I came to below things. 4.1 > kernel version onwards "nr_pages = min(sdio->pages_in_io, > bio_get_nr_vecs(map_bh->b_bdev))" has been removed which > (bio_get_nr_vecs) was considering max_sectors_kb of queue which was > 104 KB for our device. > > Presently new code is something like "nr_pages = > min(sdio->pages_in_io, BIO_MAX_PAGES)" which is sending 256 KB > (BIO_MAX_PAGES) of BIO size to our device which we are not supporting. > > > So from some documentation I found out that 256 KB of bio size is the > fix (from 4.x kernel) and that has to support by any drive. Please > let me know is there any way to change BIO size worth of 104 KB from > 256 KB or any other way to register our BIO size with kernel or any > other area to look in to ?. I'm assuming this is some not-open driver, and I'm also assuming that you are bypassing the proper API and using make_request_fn. In which case you are missing a call to blk_queue_split(). -- Jens Axboe
