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| author | Eric Biggers <ebiggers@google.com> | 2019-12-31 12:10:26 -0600 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2020-01-14 12:51:12 -0800 |
| commit | 2d8f7f119b0b2ce5e7ff0e8024b0763bf42b99c9 (patch) | |
| tree | f08d5430b86b860cc5c4020de52ba7ed21e25c0d /fs/crypto/crypto.c | |
| parent | 796f12d742653028a1520cce3a76035c86e2ebf9 (diff) | |
| download | linux-2d8f7f119b0b2ce5e7ff0e8024b0763bf42b99c9.tar.bz2 | |
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: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/crypto/crypto.c')
| -rw-r--r-- | fs/crypto/crypto.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index fcc6ca792ba2..1ecaac7ee3cb 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -138,7 +138,7 @@ 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 @@ -148,6 +148,11 @@ 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, |