Re: [PATCH v4 3/7] iomap: support direct I/O with fscrypt using blk-crypto

Jaegeuk Kim
2020-07-22T17:06:58Z

On 07/20, Satya Tangirala wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Wire up iomap direct I/O with the fscrypt additions for direct I/O.
> This allows ext4 to support direct I/O on encrypted files when inline
> encryption is enabled.
>
> This change consists of two parts:
>
> - Set a bio_crypt_ctx on bios for encrypted files, so that the file
> contents get encrypted (or decrypted).
>
> - Ensure that encryption data unit numbers (DUNs) are contiguous within
> each bio. Use the new function fscrypt_limit_io_pages() for this,
> since the iomap code works directly with logical ranges and thus
> doesn't have a chance to call fscrypt_mergeable_bio() on each page.
>
> Note that fscrypt_limit_io_pages() is normally a no-op, as normally the
> DUNs simply increment along with the logical blocks. But it's needed to
> handle an edge case in one of the fscrypt IV generation methods.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Co-developed-by: Satya Tangirala <satyat@google.com>
> Signed-off-by: Satya Tangirala <satyat@google.com>

Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>

> ---
> fs/iomap/direct-io.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index ec7b78e6feca..12064daa3e3d 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -6,6 +6,7 @@
> #include <linux/module.h>
> #include <linux/compiler.h>
> #include <linux/fs.h>
> +#include <linux/fscrypt.h>
> #include <linux/iomap.h>
> #include <linux/backing-dev.h>
> #include <linux/uio.h>
> @@ -183,11 +184,16 @@ static void
> iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
> unsigned len)
> {
> + struct inode *inode = file_inode(dio->iocb->ki_filp);
> struct page *page = ZERO_PAGE(0);
> int flags = REQ_SYNC | REQ_IDLE;
> struct bio *bio;
>
> bio = bio_alloc(GFP_KERNEL, 1);
> +
> + /* encrypted direct I/O is guaranteed to be fs-block aligned */
> + WARN_ON_ONCE(fscrypt_needs_contents_encryption(inode));
> +
> bio_set_dev(bio, iomap->bdev);
> bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
> bio->bi_private = dio;
> @@ -253,6 +259,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> ret = nr_pages;
> goto out;
> }
> + nr_pages = fscrypt_limit_io_pages(inode, pos, nr_pages);
>
> if (need_zeroout) {
> /* zero out from the start of the block to the write offset */
> @@ -270,6 +277,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> }
>
> bio = bio_alloc(GFP_KERNEL, nr_pages);
> + fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
> + GFP_KERNEL);
> bio_set_dev(bio, iomap->bdev);
> bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
> bio->bi_write_hint = dio->iocb->ki_hint;
> @@ -306,9 +315,10 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> dio->size += n;
> copied += n;
>
> - nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
> iomap_dio_submit_bio(dio, iomap, bio, pos);
> pos += n;
> + nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
> + nr_pages = fscrypt_limit_io_pages(inode, pos, nr_pages);
> } while (nr_pages);
>
> /*
> --
> 2.28.0.rc0.105.gf9edc3c819-goog