crypto: shash - remove shash_desc::flags

The flags field in 'struct shash_desc' never actually does anything.
The only ostensibly supported flag is CRYPTO_TFM_REQ_MAY_SLEEP.
However, no shash algorithm ever sleeps, making this flag a no-op.

With this being the case, inevitably some users who can't sleep wrongly
pass MAY_SLEEP.  These would all need to be fixed if any shash algorithm
actually started sleeping.  For example, the shash_ahash_*() functions,
which wrap a shash algorithm with the ahash API, pass through MAY_SLEEP
from the ahash API to the shash API.  However, the shash functions are
called under kmap_atomic(), so actually they're assumed to never sleep.

Even if it turns out that some users do need preemption points while
hashing large buffers, we could easily provide a helper function
crypto_shash_update_large() which divides the data into smaller chunks
and calls crypto_shash_update() and cond_resched() for each chunk.  It's
not necessary to have a flag in 'struct shash_desc', nor is it necessary
to make individual shash algorithms aware of this at all.

Therefore, remove shash_desc::flags, and document that the
crypto_shash_*() functions can be called from any context.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 8 insertions, 3 deletions

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 3b31c1b349ae..d21bea2c4382 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -146,8 +146,6 @@ struct ahash_alg {
 
 struct shash_desc {
 	struct crypto_shash *tfm;
-	u32 flags;
-
 	void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };
 
@@ -819,6 +817,7 @@ static inline void *shash_desc_ctx(struct shash_desc *desc)
  * cipher handle must point to a keyed message digest cipher in order for this
  * function to succeed.
  *
+ * Context: Any context.
  * Return: 0 if the setting of the key was successful; < 0 if an error occurred
  */
 int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
@@ -835,6 +834,7 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
  * crypto_shash_update and crypto_shash_final. The parameters have the same
  * meaning as discussed for those separate three functions.
  *
+ * Context: Any context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
@@ -850,6 +850,7 @@ int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
  * caller-allocated output buffer out which must have sufficient size (e.g. by
  * calling crypto_shash_descsize).
  *
+ * Context: Any context.
  * Return: 0 if the export creation was successful; < 0 if an error occurred
  */
 static inline int crypto_shash_export(struct shash_desc *desc, void *out)
@@ -866,6 +867,7 @@ static inline int crypto_shash_export(struct shash_desc *desc, void *out)
  * the input buffer. That buffer should have been generated with the
  * crypto_ahash_export function.
  *
+ * Context: Any context.
  * Return: 0 if the import was successful; < 0 if an error occurred
  */
 static inline int crypto_shash_import(struct shash_desc *desc, const void *in)
@@ -886,6 +888,7 @@ static inline int crypto_shash_import(struct shash_desc *desc, const void *in)
  * operational state handle. Any potentially existing state created by
  * previous operations is discarded.
  *
+ * Context: Any context.
  * Return: 0 if the message digest initialization was successful; < 0 if an
  *	   error occurred
  */
@@ -907,6 +910,7 @@ static inline int crypto_shash_init(struct shash_desc *desc)
  *
  * Updates the message digest state of the operational state handle.
  *
+ * Context: Any context.
  * Return: 0 if the message digest update was successful; < 0 if an error
  *	   occurred
  */
@@ -923,6 +927,7 @@ int crypto_shash_update(struct shash_desc *desc, const u8 *data,
  * into the output buffer. The caller must ensure that the output buffer is
  * large enough by using crypto_shash_digestsize.
  *
+ * Context: Any context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
@@ -939,6 +944,7 @@ int crypto_shash_final(struct shash_desc *desc, u8 *out);
  * crypto_shash_update and crypto_shash_final. The parameters have the same
  * meaning as discussed for those separate functions.
  *
+ * Context: Any context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 0f919d5fe84f..c2ffff5f9ae2 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1606,7 +1606,6 @@ static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
 		JBD_MAX_CHECKSUM_SIZE);
 
 	desc.shash.tfm = journal->j_chksum_driver;
-	desc.shash.flags = 0;
 	*(u32 *)desc.ctx = crc;
 
 	err = crypto_shash_update(&desc.shash, address, length);