From: Chandan Rajendra <chandan@xxxxxxxxxxxxx>
In ext4_block_write_begin(), only decrypt the blocks that actually need
to be decrypted (up to two blocks which intersect the boundaries of the
region that will be written to), rather than assuming blocksize ==
PAGE_SIZE and decrypting the whole page.
This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxx>
(EB: rebase onto previous changes, improve the commit message,
and move the check for encrypted inode)
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/ext4/inode.c | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0e6536a22a465..8b3ea9c8ac988 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1164,8 +1164,9 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
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;
+ struct buffer_head *bh, *head, *wait[2];
+ int nr_wait = 0;
+ int i;
BUG_ON(!PageLocked(page));
BUG_ON(from > PAGE_SIZE);
@@ -1217,24 +1218,30 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
!buffer_unwritten(bh) &&
(block_start < from || block_end > to)) {
ll_rw_block(REQ_OP_READ, 0, 1, &bh);
- *wait_bh++ = bh;
- decrypt = IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode);
+ wait[nr_wait++] = bh;
}
}
/*
* If we issued read requests, let them complete.
*/
- while (wait_bh > wait) {
- wait_on_buffer(*--wait_bh);
- if (!buffer_uptodate(*wait_bh))
+ for (i = 0; i < nr_wait; i++) {
+ wait_on_buffer(wait[i]);
+ if (!buffer_uptodate(wait[i]))
err = -EIO;
}
if (unlikely(err)) {
page_zero_new_buffers(page, from, to);
- } else if (decrypt) {
- err = fscrypt_decrypt_pagecache_blocks(page, PAGE_SIZE, 0);
- if (err)
- clear_buffer_uptodate(*wait_bh);
+ } else if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode)) {
+ for (i = 0; i < nr_wait; i++) {
+ int err2;
+
+ err2 = fscrypt_decrypt_pagecache_blocks(page, blocksize,
+ bh_offset(wait[i]));
+ if (err2) {
+ clear_buffer_uptodate(wait[i]);
+ err = err2;
+ }
+ }
}
return err;
--
2.21.0.1020.gf2820cf01a-goog
