From: Eric Biggers <ebiggers@xxxxxxxxxx>
As an optimization, don't encrypt blocks fully beyond i_size, since
those definitely won't need to be written out. Also add a comment.
This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.
This is based on work by Chandan Rajendra.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/ext4/page-io.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 457ddf051608f..ab843ad89df2f 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -468,11 +468,19 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
bh = head = page_buffers(page);
+ /*
+ * If any blocks are being written to an encrypted file, encrypt them
+ * into a bounce page. For simplicity, just encrypt until the last
+ * block which might be needed. This may cause some unneeded blocks
+ * (e.g. holes) to be unnecessarily encrypted, but this is rare and
+ * can't happen in the common case of blocksize == PAGE_SIZE.
+ */
if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode) && nr_to_submit) {
gfp_t gfp_flags = GFP_NOFS;
+ unsigned int enc_bytes = round_up(len, i_blocksize(inode));
retry_encrypt:
- bounce_page = fscrypt_encrypt_pagecache_blocks(page, PAGE_SIZE,
+ bounce_page = fscrypt_encrypt_pagecache_blocks(page, enc_bytes,
0, gfp_flags);
if (IS_ERR(bounce_page)) {
ret = PTR_ERR(bounce_page);
--
2.21.0.593.g511ec345e18-goog
