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Commit 6fe9354e authored by Eric Biggers's avatar Eric Biggers Committed by Jaegeuk Kim
Browse files

fscrypt: document gfp_flags for bounce page allocation 

Document that fscrypt_encrypt_pagecache_blocks() allocates the bounce
page from a mempool, and document what this means for the @gfp_flags
argument.

Link: https://lore.kernel.org/r/20191231181026.47400-1-ebiggers@kernel.org


Reviewed-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent 7df05e52

fs/crypto/crypto.c

+6 −1
Original line number Diff line number Diff line
@@ -137,7 +137,7 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw, 
 *		multiple of the filesystem's block size.

 * @offs:      Byte offset within @page of the first block to encrypt.  Must be

 *		a multiple of the filesystem's block size.

 * @gfp_flags: Memory allocation flags

 * @gfp_flags: Memory allocation flags.  See details below.

 *

 * A new bounce page is allocated, and the specified block(s) are encrypted into

 * it.  In the bounce page, the ciphertext block(s) will be located at the same
@@ -147,6 +147,11 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw, 
 *

 * This is for use by the filesystem's ->writepages() method.

 *

 * The bounce page allocation is mempool-backed, so it will always succeed when

 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS.  However,

 * only the first page of each bio can be allocated this way.  To prevent

 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.

 *

 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure

 */

struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,