ext4 crypto: implement the ext4 encryption write path
Pulls block_write_begin() into fs/ext4/inode.c because it might need
to do a low-level read of the existing data, in which case we need to
decrypt it.
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Ildar Muslukhov <ildarm@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index cd30091..7c4527e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -886,6 +886,95 @@
static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
+
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
+ get_block_t *get_block)
+{
+ unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+ unsigned to = from + len;
+ struct inode *inode = page->mapping->host;
+ unsigned block_start, block_end;
+ sector_t block;
+ int err = 0;
+ unsigned blocksize = inode->i_sb->s_blocksize;
+ unsigned bbits;
+ struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
+ bool decrypt = false;
+
+ BUG_ON(!PageLocked(page));
+ BUG_ON(from > PAGE_CACHE_SIZE);
+ BUG_ON(to > PAGE_CACHE_SIZE);
+ BUG_ON(from > to);
+
+ if (!page_has_buffers(page))
+ create_empty_buffers(page, blocksize, 0);
+ head = page_buffers(page);
+ bbits = ilog2(blocksize);
+ block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
+
+ for (bh = head, block_start = 0; bh != head || !block_start;
+ block++, block_start = block_end, bh = bh->b_this_page) {
+ block_end = block_start + blocksize;
+ if (block_end <= from || block_start >= to) {
+ if (PageUptodate(page)) {
+ if (!buffer_uptodate(bh))
+ set_buffer_uptodate(bh);
+ }
+ continue;
+ }
+ if (buffer_new(bh))
+ clear_buffer_new(bh);
+ if (!buffer_mapped(bh)) {
+ WARN_ON(bh->b_size != blocksize);
+ err = get_block(inode, block, bh, 1);
+ if (err)
+ break;
+ if (buffer_new(bh)) {
+ unmap_underlying_metadata(bh->b_bdev,
+ bh->b_blocknr);
+ if (PageUptodate(page)) {
+ clear_buffer_new(bh);
+ set_buffer_uptodate(bh);
+ mark_buffer_dirty(bh);
+ continue;
+ }
+ if (block_end > to || block_start < from)
+ zero_user_segments(page, to, block_end,
+ block_start, from);
+ continue;
+ }
+ }
+ if (PageUptodate(page)) {
+ if (!buffer_uptodate(bh))
+ set_buffer_uptodate(bh);
+ continue;
+ }
+ if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
+ !buffer_unwritten(bh) &&
+ (block_start < from || block_end > to)) {
+ ll_rw_block(READ, 1, &bh);
+ *wait_bh++ = bh;
+ decrypt = ext4_encrypted_inode(inode) &&
+ S_ISREG(inode->i_mode);
+ }
+ }
+ /*
+ * If we issued read requests, let them complete.
+ */
+ while (wait_bh > wait) {
+ wait_on_buffer(*--wait_bh);
+ if (!buffer_uptodate(*wait_bh))
+ err = -EIO;
+ }
+ if (unlikely(err))
+ page_zero_new_buffers(page, from, to);
+ else if (decrypt)
+ err = ext4_decrypt_one(inode, page);
+ return err;
+}
+#endif
+
static int ext4_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
@@ -948,11 +1037,19 @@
/* In case writeback began while the page was unlocked */
wait_for_stable_page(page);
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ if (ext4_should_dioread_nolock(inode))
+ ret = ext4_block_write_begin(page, pos, len,
+ ext4_get_block_write);
+ else
+ ret = ext4_block_write_begin(page, pos, len,
+ ext4_get_block);
+#else
if (ext4_should_dioread_nolock(inode))
ret = __block_write_begin(page, pos, len, ext4_get_block_write);
else
ret = __block_write_begin(page, pos, len, ext4_get_block);
-
+#endif
if (!ret && ext4_should_journal_data(inode)) {
ret = ext4_walk_page_buffers(handle, page_buffers(page),
from, to, NULL,
@@ -2574,7 +2671,12 @@
/* In case writeback began while the page was unlocked */
wait_for_stable_page(page);
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ ret = ext4_block_write_begin(page, pos, len,
+ ext4_da_get_block_prep);
+#else
ret = __block_write_begin(page, pos, len, ext4_da_get_block_prep);
+#endif
if (ret < 0) {
unlock_page(page);
ext4_journal_stop(handle);
@@ -3032,6 +3134,9 @@
get_block_func = ext4_get_block_write;
dio_flags = DIO_LOCKING;
}
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ BUG_ON(ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode));
+#endif
if (IS_DAX(inode))
ret = dax_do_io(rw, iocb, inode, iter, offset, get_block_func,
ext4_end_io_dio, dio_flags);
@@ -3096,6 +3201,11 @@
size_t count = iov_iter_count(iter);
ssize_t ret;
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode))
+ return 0;
+#endif
+
/*
* If we are doing data journalling we don't support O_DIRECT
*/