Forgot, to put it into a context, I'm working on an experimental device mapper target, so this is happening inside a target, after I've received a bio and sent out DM_MAPIO_SUBMITTED... ----- Original Message ----- From: Enoch Root <enokhroot@xxxxxxxxx> To: "dm-devel@xxxxxxxxxx" <dm-devel@xxxxxxxxxx> Cc: Sent: Thursday, May 22, 2014 3:49 AM Subject: Re-using bio Hi, Is it legal to re-use a bio that has been through a call to generic_make_request? Assuming I want to perform read-modify-write, where modify part also comes from some other part of the disk, would it be legal to 1) alloc bio, add e.g. 4 pages to it, set the starting sector 2) call generic_make_request to read data 3) assuming I want to change page 3, clone the bio, change idx, to point to page 3, set the starting sector and the size 4) call generic_make_request to modify page 3 by reading data into it 5) change the direction of the original bio from read to write 6) call generic_make_request to write it back to disk I have already attempted doing this, but I hit BUG_ON(bio->bi_next) in generic_make_request. Am am doing something wrong or this is not how it should be done? If so, please let me know how to do it properly. Thanks! -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
