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fscrypt: optimize fscrypt_zeroout_range()

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Currently fscrypt_zeroout_range() issues and waits on a bio for each
block it writes, which makes it very slow.

Optimize it to write up to 16 pages at a time instead.

Also add a function comment, and improve reliability by allowing the
allocations of the bio and the first ciphertext page to wait on the
corresponding mempools.

Link: https://lore.kernel.org/r/20191226160813.53182-1-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2019-12-26 10:08:13 -06:00
parent f4a0b08b39
commit 796f12d742
1 changed files with 81 additions and 31 deletions
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112
fs/crypto/bio.c
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@ -41,51 +41,101 @@ void fscrypt_decrypt_bio(struct bio *bio)
}
EXPORT_SYMBOL(fscrypt_decrypt_bio);
/**
* fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
* @inode: the file's inode
* @lblk: the first file logical block to zero out
* @pblk: the first filesystem physical block to zero out
* @len: number of blocks to zero out
*
* Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
* ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
* both logically and physically contiguous. It's also assumed that the
* filesystem only uses a single block device, ->s_bdev.
*
* Note that since each block uses a different IV, this involves writing a
* different ciphertext to each block; we can't simply reuse the same one.
*
* Return: 0 on success; -errno on failure.
*/
int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
sector_t pblk, unsigned int len)
sector_t pblk, unsigned int len)
{
const unsigned int blockbits = inode->i_blkbits;
const unsigned int blocksize = 1 << blockbits;
struct page *ciphertext_page;
const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
struct page *pages[16]; /* write up to 16 pages at a time */
unsigned int nr_pages;
unsigned int i;
unsigned int offset;
struct bio *bio;
int ret, err = 0;
int ret, err;
ciphertext_page = fscrypt_alloc_bounce_page(GFP_NOWAIT);
if (!ciphertext_page)
return -ENOMEM;
if (len == 0)
return 0;
while (len--) {
err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
ZERO_PAGE(0), ciphertext_page,
blocksize, 0, GFP_NOFS);
if (err)
goto errout;
BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_PAGES);
nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
(len + blocks_per_page - 1) >> blocks_per_page_bits);
bio = bio_alloc(GFP_NOWAIT, 1);
if (!bio) {
err = -ENOMEM;
goto errout;
}
/*
* We need at least one page for ciphertext. Allocate the first one
* from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
*
* Any additional page allocations are allowed to fail, as they only
* help performance, and waiting on the mempool for them could deadlock.
*/
for (i = 0; i < nr_pages; i++) {
pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
GFP_NOWAIT | __GFP_NOWARN);
if (!pages[i])
break;
}
nr_pages = i;
if (WARN_ON(nr_pages <= 0))
return -EINVAL;
/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
bio = bio_alloc(GFP_NOFS, nr_pages);
do {
bio_set_dev(bio, inode->i_sb->s_bdev);
bio->bi_iter.bi_sector = pblk << (blockbits - 9);
bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
ret = bio_add_page(bio, ciphertext_page, blocksize, 0);
if (WARN_ON(ret != blocksize)) {
/* should never happen! */
bio_put(bio);
err = -EIO;
goto errout;
}
i = 0;
offset = 0;
do {
err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
ZERO_PAGE(0), pages[i],
blocksize, offset, GFP_NOFS);
if (err)
goto out;
lblk++;
pblk++;
len--;
offset += blocksize;
if (offset == PAGE_SIZE || len == 0) {
ret = bio_add_page(bio, pages[i++], offset, 0);
if (WARN_ON(ret != offset)) {
err = -EIO;
goto out;
}
offset = 0;
}
} while (i != nr_pages && len != 0);
err = submit_bio_wait(bio);
bio_put(bio);
if (err)
goto errout;
lblk++;
pblk++;
}
goto out;
bio_reset(bio);
} while (len != 0);
err = 0;
errout:
fscrypt_free_bounce_page(ciphertext_page);
out:
bio_put(bio);
for (i = 0; i < nr_pages; i++)
fscrypt_free_bounce_page(pages[i]);
return err;
}
EXPORT_SYMBOL(fscrypt_zeroout_range);