On 05/19/2009 03:49 PM, Jens Axboe wrote: > On Tue, May 19 2009, Boaz Harrosh wrote: >> + * WARNING: When allocating/cloning a bio-chain, careful consideration should be >> + * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for >> + * anything but the first bio in the chain. Otherwise you risk deadlocking, >> + * waiting for a bio to be returned to the pool, which will never return, since >> + * it was not submitted yet. > > Perhaps something like: > > Otherwise you risk waiting for IO completion of a bio that hasn't been > submitted yet, thus resulting in a deadlock. > >> + * Alternatively bios should be allocated using bio_kmalloc only. >> + * If possible a long IO should be split into smaller parts when allocation >> + * fails. Partial allocation should not be an error, or you risk a live-lock. >> */ >> struct request *blk_make_request(struct request_queue *q, struct bio *bio, >> gfp_t gfp_mask) > > Alternatively bios should be allocated using bio_kmalloc() instead of > bio_alloc(), as that avoids the mempool deadlock. If possible a big IO > should be ... > Thanks Jens makes much more sense. I'm posting as reply to original patch (with version 2 at title). I'm also reposting a small forgoten patch that belongs to Tejun's batch. Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
