Commit 31fb992c authored by Eric Biggers's avatar Eric Biggers Committed by Theodore Ts'o
Browse files

fs/buffer.c: support fscrypt in block_read_full_page() 



After each filesystem block (as represented by a buffer_head) has been
read from disk by block_read_full_page(), decrypt it if needed.  The
decryption is done on the fscrypt_read_workqueue.

This is the final change needed to support ext4 encryption with
blocksize != PAGE_SIZE, and it's a fairly small change now that
CONFIG_FS_ENCRYPTION is a bool and fs/crypto/ exposes functions to
decrypt individual blocks and to enqueue work on the fscrypt workqueue.

Don't try to add fs-verity support yet, as the fs/verity/ support layer
isn't ready for sub-page blocks yet.  Just add fscrypt support for now.

Almost all the new code is compiled away when CONFIG_FS_ENCRYPTION=n.

Cc: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20191023033312.361355-2-ebiggers@kernel.org


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 4d06bfb9

fs/buffer.c

+43 −5
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <linux/pagevec.h>

#include <linux/sched/mm.h>

#include <trace/events/block.h>

#include <linux/fscrypt.h>



static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);

static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
@@ -246,10 +247,6 @@ out: 
	return ret;

}



/*

 * I/O completion handler for block_read_full_page() - pages

 * which come unlocked at the end of I/O.

 */

static void end_buffer_async_read(struct buffer_head *bh, int uptodate)

{

	unsigned long flags;
@@ -307,6 +304,47 @@ still_busy: 
	return;

}



struct decrypt_bh_ctx {

	struct work_struct work;

	struct buffer_head *bh;

};



static void decrypt_bh(struct work_struct *work)

{

	struct decrypt_bh_ctx *ctx =

		container_of(work, struct decrypt_bh_ctx, work);

	struct buffer_head *bh = ctx->bh;

	int err;



	err = fscrypt_decrypt_pagecache_blocks(bh->b_page, bh->b_size,

					       bh_offset(bh));

	end_buffer_async_read(bh, err == 0);

	kfree(ctx);

}



/*

 * I/O completion handler for block_read_full_page() - pages

 * which come unlocked at the end of I/O.

 */

static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)

{

	/* Decrypt if needed */

	if (uptodate && IS_ENABLED(CONFIG_FS_ENCRYPTION) &&

	    IS_ENCRYPTED(bh->b_page->mapping->host) &&

	    S_ISREG(bh->b_page->mapping->host->i_mode)) {

		struct decrypt_bh_ctx *ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);



		if (ctx) {

			INIT_WORK(&ctx->work, decrypt_bh);

			ctx->bh = bh;

			fscrypt_enqueue_decrypt_work(&ctx->work);

			return;

		}

		uptodate = 0;

	}

	end_buffer_async_read(bh, uptodate);

}



/*

 * Completion handler for block_write_full_page() - pages which are unlocked

 * during I/O, and which have PageWriteback cleared upon I/O completion.
@@ -379,7 +417,7 @@ EXPORT_SYMBOL(end_buffer_async_write); 
 */

static void mark_buffer_async_read(struct buffer_head *bh)

{

	bh->b_end_io = end_buffer_async_read;

	bh->b_end_io = end_buffer_async_read_io;

	set_buffer_async_read(bh);

}

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