From 796f12d742653028a1520cce3a76035c86e2ebf9 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 26 Dec 2019 10:08:13 -0600 Subject: [PATCH] fscrypt: optimize fscrypt_zeroout_range() 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 Signed-off-by: Eric Biggers --- fs/crypto/bio.c | 112 ++++++++++++++++++++++++++++++++++-------------- 1 file changed, 81 insertions(+), 31 deletions(-) diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c index b88d417e186e..4fa18fff9c4e 100644 --- a/fs/crypto/bio.c +++ b/fs/crypto/bio.c @@ -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);