From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/buffer.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 43 insertions(+), 5 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 86a38b979323..d39838090b22 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -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 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
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 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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);
}
--
2.23.0
