Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-29 14:21:47 +00:00
Code Issues Packages Projects Releases Wiki Activity

ext4: decrypt only the needed blocks in ext4_block_write_begin()

Browse Source 
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@linux.ibm.com>
(EB: rebase onto previous changes, improve the commit message,
 and move the check for encrypted inode)
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Chandan Rajendra 2019-05-20 09:29:50 -07:00 committed by Eric Biggers
parent 7e0785fce1
commit 0b578f358a
1 changed files with 18 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
fs/ext4/inode.c
View File

@ -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;