3dbb5eb9a3
Previously we allocated bounce pages using a combination of alloc_page() and mempool_alloc() with the __GFP_WAIT bit set. Instead, use mempool_alloc() with GFP_NOWAIT. The mempool_alloc() function will try using alloc_pages() initially, and then only use the mempool reserve of pages if alloc_pages() is unable to fulfill the request. This minimizes the the impact on the mm layer when we need to do a large amount of writeback of encrypted files, as Jaeguk Kim had reported that under a heavy fio workload on a system with restricted amounts memory (which unfortunately, includes many mobile handsets), he had observed the the OOM killer getting triggered several times. Using GFP_NOWAIT If the mempool_alloc() function fails, we will retry the page writeback at a later time; the function of the mempool is to ensure that we can writeback at least 32 pages at a time, so we can more efficiently dispatch I/O under high memory pressure situations. In the future we should make this be a tunable so we can determine the best tradeoff between permanently sequestering memory and the ability to quickly launder pages so we can free up memory quickly when necessary. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
160 lines
4 KiB
C
160 lines
4 KiB
C
/*
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* linux/fs/ext4/ext4_crypto.h
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*
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* Copyright (C) 2015, Google, Inc.
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*
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* This contains encryption header content for ext4
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*
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* Written by Michael Halcrow, 2015.
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*/
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#ifndef _EXT4_CRYPTO_H
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#define _EXT4_CRYPTO_H
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#include <linux/fs.h>
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#define EXT4_KEY_DESCRIPTOR_SIZE 8
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/* Policy provided via an ioctl on the topmost directory */
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struct ext4_encryption_policy {
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char version;
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char contents_encryption_mode;
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char filenames_encryption_mode;
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char flags;
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char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
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} __attribute__((__packed__));
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#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
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#define EXT4_KEY_DERIVATION_NONCE_SIZE 16
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#define EXT4_POLICY_FLAGS_PAD_4 0x00
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#define EXT4_POLICY_FLAGS_PAD_8 0x01
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#define EXT4_POLICY_FLAGS_PAD_16 0x02
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#define EXT4_POLICY_FLAGS_PAD_32 0x03
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#define EXT4_POLICY_FLAGS_PAD_MASK 0x03
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#define EXT4_POLICY_FLAGS_VALID 0x03
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/**
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* Encryption context for inode
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*
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* Protector format:
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* 1 byte: Protector format (1 = this version)
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* 1 byte: File contents encryption mode
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* 1 byte: File names encryption mode
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* 1 byte: Reserved
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* 8 bytes: Master Key descriptor
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* 16 bytes: Encryption Key derivation nonce
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*/
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struct ext4_encryption_context {
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char format;
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char contents_encryption_mode;
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char filenames_encryption_mode;
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char flags;
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char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
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char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
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} __attribute__((__packed__));
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/* Encryption parameters */
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#define EXT4_XTS_TWEAK_SIZE 16
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#define EXT4_AES_128_ECB_KEY_SIZE 16
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#define EXT4_AES_256_GCM_KEY_SIZE 32
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#define EXT4_AES_256_CBC_KEY_SIZE 32
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#define EXT4_AES_256_CTS_KEY_SIZE 32
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#define EXT4_AES_256_XTS_KEY_SIZE 64
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#define EXT4_MAX_KEY_SIZE 64
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#define EXT4_KEY_DESC_PREFIX "ext4:"
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#define EXT4_KEY_DESC_PREFIX_SIZE 5
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/* This is passed in from userspace into the kernel keyring */
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struct ext4_encryption_key {
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__u32 mode;
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char raw[EXT4_MAX_KEY_SIZE];
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__u32 size;
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} __attribute__((__packed__));
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struct ext4_crypt_info {
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char ci_data_mode;
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char ci_filename_mode;
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char ci_flags;
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struct crypto_ablkcipher *ci_ctfm;
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struct key *ci_keyring_key;
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char ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
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};
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#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
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#define EXT4_WRITE_PATH_FL 0x00000002
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struct ext4_crypto_ctx {
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union {
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struct {
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struct page *bounce_page; /* Ciphertext page */
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struct page *control_page; /* Original page */
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} w;
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struct {
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struct bio *bio;
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struct work_struct work;
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} r;
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struct list_head free_list; /* Free list */
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};
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char flags; /* Flags */
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char mode; /* Encryption mode for tfm */
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};
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struct ext4_completion_result {
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struct completion completion;
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int res;
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};
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#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
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struct ext4_completion_result ecr = { \
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COMPLETION_INITIALIZER((ecr).completion), 0 }
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static inline int ext4_encryption_key_size(int mode)
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{
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switch (mode) {
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case EXT4_ENCRYPTION_MODE_AES_256_XTS:
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return EXT4_AES_256_XTS_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_GCM:
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return EXT4_AES_256_GCM_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_CBC:
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return EXT4_AES_256_CBC_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_CTS:
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return EXT4_AES_256_CTS_KEY_SIZE;
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default:
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BUG();
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}
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return 0;
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}
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#define EXT4_FNAME_NUM_SCATTER_ENTRIES 4
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#define EXT4_CRYPTO_BLOCK_SIZE 16
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#define EXT4_FNAME_CRYPTO_DIGEST_SIZE 32
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struct ext4_str {
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unsigned char *name;
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u32 len;
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};
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/**
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* For encrypted symlinks, the ciphertext length is stored at the beginning
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* of the string in little-endian format.
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*/
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struct ext4_encrypted_symlink_data {
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__le16 len;
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char encrypted_path[1];
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} __attribute__((__packed__));
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/**
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* This function is used to calculate the disk space required to
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* store a filename of length l in encrypted symlink format.
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*/
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static inline u32 encrypted_symlink_data_len(u32 l)
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{
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if (l < EXT4_CRYPTO_BLOCK_SIZE)
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l = EXT4_CRYPTO_BLOCK_SIZE;
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return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
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}
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#endif /* _EXT4_CRYPTO_H */
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