Messages in this thread | | | From | Badari Pulavarty <> | Subject | Re: patch: aio + bio for raw io | Date | Fri, 8 Feb 2002 13:07:58 -0800 (PST) |
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> > Quick message: this patch makes aio use bio directly for brw_kvec_async. > This is against yesterday's patchset. Comments? > > -ben
Hi Ben,
I am looking at the 2.5 patch you sent out. I have few questions/comments:
1) brw_kvec_async() does not seem to split IO at BIO_MAX_SIZE. I thought each bio can handle only BIO_MAX_SIZE (ll_rw_kio() is creating one bio for each BIO_MAX_SIZE IO).
And also, currently BIO_MAX_SIZE is only 64K. Infact, if I try to issue 64K IO using submit_bio(), I get following BUG() on my QLOGIC controller.
kernel BUG at ll_rw_blk.c:1336
Code is: BUG_ON(bio_sectors(bio) > q->max_sectors);
bio_sectors(bio) is 128 q->max_sectors is 64 (for QLOGIC ISP)
Is this going to be fixed ? Can "bio" should be able to handle any size IO ? Or we should issue create a new bio for each BIO_MAX_SIZE IO ?
2) Could you please make map_user_kvec() generic enough to handle mapping of mutliple iovecs to single kvec (to handle readv/writev). I think this is a very easy change:
* Add alloc_kvec() and take out the kmalloc() from map_user_kvec(). * Change map_user_kvec() to start mapping from kvec->veclet[kvec->nr] instead of kvec->veclet[0]
This way allocation for kvec to hold all the iovecs can be done at higher level and map_user_kvec() can be called in a loop once for each iovec.
Then we can add read/writev support for RAW IO very easily. I am looking at making use of kvec for RAW IO and also add support for readv/writev. (I already sent a patch to do this - but since you ported all your AIO work to 2.5, we can work on your infrastructure :)
Please let me know what you think.
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