Hi I've found out that a lot of hardware crypto drivers use GFP_ATOMIC. Some of them switch between GFP_ATOMIC and GFP_KERNEL based on the flag CRYPTO_TFM_REQ_MAY_SLEEP. dm-crypt and dm-integrity don't use CRYPTO_TFM_REQ_MAY_SLEEP (because GFP_KERNEL allocation requests can recurse back to the block device drivers and cause deadlocks). So, basically, the crypto requests submitted by dm-crypt and dm-integrity can fail anytime. I'd like to ask, how to handle these random -ENOMEM return codes. If we pass -ENOMEM back to the block device stack, it could cause random I/O errors and data corruption. The question is - if the crypto request returns -ENOMEM, could we sleep and retry it? I thought about it - the problem could be, if the crypto requests proceeds hafway through and then returns -ENOMEM, and if we retried it, it would cause data corruption, because part of the data would be decrypted twice. Is it safe to assume that when we get -ENOMEM, the crypto driver didn't modify anything? Do you have another idea how to solve this problem? Mikulas
