ext4: encrypt only up to last block in ext4_bio_write_page() (6e4b73bc) · Commits · 戴 / test

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. Reviewed-by:

Chandan Rajendra <chandan@linux.ibm.com> Signed-off-by:

Eric Biggers <ebiggers@google.com>

fs/ext4/page-io.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -467,11 +467,19 @@ 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);

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