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Date: Wed, 8 Apr 2015 12:51:04 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>,
jaegeuk@...nel.org, mhalcrow@...gle.com,
Ildar Muslukhov <ildarm@...gle.com>
Subject: Re: [PATCH 13/22] ext4 crypto: implement the ext4 decryption read path
On Apr 2, 2015, at 4:10 PM, Theodore Ts'o <tytso@....edu> wrote:
>
> From: Michael Halcrow <mhalcrow@...gle.com>
>
> Change-Id: Ie9c043a132a01da60d1617662cd30307639f5599
> Signed-off-by: Michael Halcrow <mhalcrow@...gle.com>
> Signed-off-by: Ildar Muslukhov <ildarm@...gle.com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
> fs/ext4/file.c | 22 +++++++++++++++----
> fs/ext4/inode.c | 10 +++++++++
> fs/ext4/readpage.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 89 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 8131be8..4cacc30 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -28,6 +28,7 @@
> #include <linux/pagevec.h>
> #include "ext4.h"
> #include "ext4_jbd2.h"
> +#include "ext4_crypto.h"
> #include "xattr.h"
> #include "acl.h"
>
> @@ -200,9 +201,15 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
>
> static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> {
> + int res = 0;
This function is using "res", the one below "ret". It would be nice to
have some consistency. "rc" is probably the most common and would be
my preference for new/modified code.
> + struct inode *inode = file->f_mapping->host;
> +
> + if (ext4_encrypted_inode(inode))
> + res = ext4_generate_encryption_key(inode);
> file_accessed(file);
> - vma->vm_ops = &ext4_file_vm_ops;
> - return 0;
> + if (!res)
> + vma->vm_ops = &ext4_file_vm_ops;
> + return res;
> }
>
> static int ext4_file_open(struct inode * inode, struct file * filp)
> @@ -212,6 +219,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
> struct vfsmount *mnt = filp->f_path.mnt;
> struct path path;
> char buf[64], *cp;
> + int ret;
>
> if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
> !(sb->s_flags & MS_RDONLY))) {
> @@ -250,11 +258,17 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
> * writing and the journal is present
> */
> if (filp->f_mode & FMODE_WRITE) {
> - int ret = ext4_inode_attach_jinode(inode);
> + ret = ext4_inode_attach_jinode(inode);
> if (ret < 0)
> return ret;
> }
> - return dquot_file_open(inode, filp);
> + ret = dquot_file_open(inode, filp);
> + if (!ret && ext4_encrypted_inode(inode)) {
> + ret = ext4_generate_encryption_key(inode);
> + if (ret)
> + ret = -EACCES;
> + }
> + return ret;
> }
>
> /*
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index dcc836c..b033405 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -39,6 +39,7 @@
> #include <linux/ratelimit.h>
> #include <linux/aio.h>
> #include <linux/bitops.h>
> +#include <linux/prefetch.h>
>
> #include "ext4_jbd2.h"
> #include "ext4_crypto.h"
> @@ -3363,6 +3364,15 @@ static int ext4_block_zero_page_range(handle_t *handle,
> /* Uhhuh. Read error. Complain and punt. */
> if (!buffer_uptodate(bh))
> goto unlock;
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> + if (S_ISREG(inode->i_mode) &&
> + ext4_encrypted_inode(inode)) {
> + /* We expect the key to be set. */
> + BUG_ON(!ext4_has_encryption_key(inode));
> + BUG_ON(blocksize != PAGE_CACHE_SIZE);
> + WARN_ON_ONCE(ext4_decrypt_one(inode, page));
> + }
> +#endif
This could avoid the #ifdef since ext4_encrypted_inode() is declared (0)
in the !CONFIG_EXT4_FS_ENCRYPTION case. The compiler will optimize out
the resulting unreachable code in that case and make this code easier
to read.
> }
> if (ext4_should_journal_data(inode)) {
> BUFFER_TRACE(bh, "get write access");
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index 9ca4dfc..8978b1d 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -43,6 +43,35 @@
>
> #include "ext4.h"
>
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +/*
> + * Call ext4_decrypt on every single page, reusing the encryption
> + * context.
> + */
> +static void completion_pages(struct work_struct *work)
> +{
> + struct ext4_crypto_ctx *ctx =
> + container_of(work, struct ext4_crypto_ctx, work);
> + struct bio *bio = ctx->bio;
> + struct bio_vec *bv;
> + int i;
> +
> + bio_for_each_segment_all(bv, bio, i) {
> + struct page *page = bv->bv_page;
> +
> + int ret = ext4_decrypt(ctx, page);
> + if (ret) {
> + WARN_ON_ONCE(1);
> + SetPageError(page);
> + } else
> + SetPageUptodate(page);
> + unlock_page(page);
> + }
> + ext4_release_crypto_ctx(ctx);
> + bio_put(bio);
> +}
> +#endif
> +
> /*
> * I/O completion handler for multipage BIOs.
> *
> @@ -60,6 +89,20 @@ static void mpage_end_io(struct bio *bio, int err)
> struct bio_vec *bv;
> int i;
>
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> + if (bio->bi_private) {
If the (bio->bi_private != NULL) check was moved to a helper function:
static inline bool ext4_bio_encrypted(struct bio *bio)
{
#ifdef CONFIG_EXT4_FS_ENCRYPTION
return unlikely(bio->bi_private != NULL);
#else
return false;
#endif
}
Then the inline #ifdefs could be removed here, since the resulting
if (false) {
...
}
block would be optimized away by the caller. It would also simplify
future changes if there is some other reason why bio->bi_private is
non-NULL besides crypto.
> + struct ext4_crypto_ctx *ctx = bio->bi_private;
> +
> + if (err)
> + ext4_release_crypto_ctx(ctx);
> + else {
The if/else should have matching {} blocks.
> + INIT_WORK(&ctx->work, completion_pages);
> + ctx->bio = bio;
> + queue_work(ext4_read_workqueue, &ctx->work);
> + return;
> + }
> + }
> +#endif
> bio_for_each_segment_all(bv, bio, i) {
> struct page *page = bv->bv_page;
>
> @@ -94,9 +137,15 @@ int ext4_mpage_readpages(struct address_space *mapping,
> unsigned page_block;
> struct block_device *bdev = inode->i_sb->s_bdev;
> int length;
> + int do_decryption = 0;
Can be bool instead of int.
> unsigned relative_block = 0;
> struct ext4_map_blocks map;
>
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> + if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode))
> + do_decryption = 1;
> +#endif
#ifdef can be removed.
> +
> map.m_pblk = 0;
> map.m_lblk = 0;
> map.m_len = 0;
> @@ -220,13 +269,24 @@ int ext4_mpage_readpages(struct address_space *mapping,
> bio = NULL;
> }
> if (bio == NULL) {
> + struct ext4_crypto_ctx *ctx = NULL;
> +
> + if (do_decryption) {
> + ctx = ext4_get_crypto_ctx(inode);
> + if (IS_ERR(ctx))
> + goto set_error_page;
> + }
> bio = bio_alloc(GFP_KERNEL,
> min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
> - if (!bio)
> + if (!bio) {
> + if (ctx)
> + ext4_release_crypto_ctx(ctx);
> goto set_error_page;
> + }
> bio->bi_bdev = bdev;
> bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
> bio->bi_end_io = mpage_end_io;
> + bio->bi_private = ctx;
> }
>
> length = first_hole << blkbits;
> --
> 2.3.0
>
> --
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Cheers, Andreas
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