Commit 489734ef authored by Eric Biggers's avatar Eric Biggers
Browse files

iomap: support direct I/O with fscrypt using blk-crypto 



Encrypted files traditionally haven't supported DIO, due to the need to
encrypt/decrypt the data.  However, when the encryption is implemented
using inline encryption (blk-crypto) instead of the traditional
filesystem-layer encryption, it is straightforward to support DIO.

Add support for this to the iomap DIO implementation by calling
fscrypt_set_bio_crypt_ctx() to set encryption contexts on the bios.

Don't check for the rare case where a DUN (crypto data unit number)
discontiguity creates a boundary that bios must not cross.  Instead,
filesystems are expected to handle this in ->iomap_begin() by limiting
the length of the mapping so that iomap doesn't have to worry about it.

Co-developed-by: default avatarSatya Tangirala <satyat@google.com>
Signed-off-by: default avatarSatya Tangirala <satyat@google.com>
Acked-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220128233940.79464-3-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent c6c89783

fs/iomap/direct-io.c

+6 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/module.h>

#include <linux/compiler.h>

#include <linux/fs.h>

#include <linux/fscrypt.h>

#include <linux/pagemap.h>

#include <linux/iomap.h>

#include <linux/backing-dev.h>
@@ -179,11 +180,14 @@ static void iomap_dio_bio_end_io(struct bio *bio) 
static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,

		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);

	fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,

				  GFP_KERNEL);

	bio_set_dev(bio, iter->iomap.bdev);

	bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);

	bio->bi_private = dio;
@@ -310,6 +314,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, 
		}



		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;