Re: [PATCH] crypto: allow to assign gfp_t for __crypto_alloc_tfm

On Tue, May 19, 2015 at 02:32:11PM +0800, Herbert Xu wrote:

On Mon, May 18, 2015 at 11:24:30PM -0700, Jaegeuk Kim wrote:

quoted

The call path in fs/ext4/crypto.c is:
 - writepage
  - ext4_encrypt
   - ext4_get_crypto_ctx
    - crypto_alloc_ablkcipher

AFAIK, this way can achieve to reduce memory footprint gracefully.
Just before submitting bios, fs allocates the required memory, and then end_io
will free them in pair.

So where does the key get generated? The crypto tfm should be
allocated when you generate the key.

In fs/ext4/crypto.c,

 - writepage
   - ext4_encrypt
     - ext4_get_crypto_ctx
       - crypto_alloc_ablkcipher
     - ext4_page_crypto
       - crypto_ablkcipher_setkey
       - ablkcipher_request_alloc(GFP_NOFS)
       - ablkcipher_request_set_crypt(PAGE_CACHE_SIZE)
       - crypto_ablkcipher_encrypt

 - end_io
   - crypto_free_tfm

Thanks,

Cheers,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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