Re: [PATCH] ecryptfs: modify write path to encrypt page in writepage

From: Tyler Hicks
Date: Thu Mar 10 2011 - 19:11:22 EST

On Tue Mar 08, 2011 at 04:26:03PM -0800, Thieu Le <thieule@xxxxxxxxxxxx> wrote:
> I've addressed the data corruption issue. I forgot to update ecryptfs_sops.drop_inode to point to NULL to indicate that ecryptfs now caches data and the cache data should be flushed to disk when the last reference to the inode is released.
>
> Commit message and updated patch below.

Thanks, Thieu. I've been testing this the last couple days and
everything is working well. I made one small change (noted inline) and
then pushed the patch to
git://git.kernel.org/pub/scm/linux/kernel/git/ecryptfs/ecryptfs-2.6.git#next

>
> ------------------------------------------------------------------------------
>
> Change the write path to encrypt the data only when the page is written to
> disk in ecryptfs_writepage. Previously, ecryptfs encrypts the page in
> ecryptfs_write_end which means that if there are multiple write requests to
> the same page, ecryptfs ends up re-encrypting that page over and over again.
> This patch minimizes the number of encryptions needed.
>
> Signed-off-by: Thieu Le <thieule@xxxxxxxxxxxx>
> ---
> fs/ecryptfs/ecryptfs_kernel.h | 1 -
> fs/ecryptfs/file.c | 9 ++++++++-
> fs/ecryptfs/main.c | 2 --
> fs/ecryptfs/mmap.c | 41 +++++++++++++++++++++++++++--------------
> fs/ecryptfs/read_write.c | 12 ++----------
> fs/ecryptfs/super.c | 3 +--
> 6 files changed, 38 insertions(+), 30 deletions(-)
>
> diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
> index dbc84ed..13517ac 100644
> --- a/fs/ecryptfs/ecryptfs_kernel.h
> +++ b/fs/ecryptfs/ecryptfs_kernel.h
> @@ -297,7 +297,6 @@ struct ecryptfs_inode_info {
> struct inode vfs_inode;
> struct inode *wii_inode;
> struct file *lower_file;
> - struct mutex lower_file_mutex;
> struct ecryptfs_crypt_stat crypt_stat;
> };
>
> diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
> index 81e10e6..9f7ce63 100644
> --- a/fs/ecryptfs/file.c
> +++ b/fs/ecryptfs/file.c
> @@ -273,7 +273,14 @@ static int ecryptfs_release(struct inode *inode, struct file *file)
> static int
> ecryptfs_fsync(struct file *file, int datasync)
> {
> - return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
> + int rc = 0;
> +
> + rc = generic_file_fsync(file, datasync);
> + if (rc)
> + goto out;
> + rc = vfs_fsync(ecryptfs_file_to_lower(file), datasync);
> +out:
> + return rc;
> }
>
> static int ecryptfs_fasync(int fd, struct file *file, int flag)
> diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
> index 758323a..63e412c 100644
> --- a/fs/ecryptfs/main.c
> +++ b/fs/ecryptfs/main.c
> @@ -122,7 +122,6 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
> ecryptfs_inode_to_private(ecryptfs_dentry->d_inode);
> int rc = 0;
>
> - mutex_lock(&inode_info->lower_file_mutex);
> if (!inode_info->lower_file) {
> struct dentry *lower_dentry;
> struct vfsmount *lower_mnt =
> @@ -138,7 +137,6 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
> inode_info->lower_file = NULL;
> }
> }
> - mutex_unlock(&inode_info->lower_file_mutex);
> return rc;
> }
>
> diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
> index cc64fca..d36829f 100644
> --- a/fs/ecryptfs/mmap.c
> +++ b/fs/ecryptfs/mmap.c
> @@ -62,6 +62,18 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
> {
> int rc;
>
> + /*
> + * Refuse to write the page out if we are called from reclaim context
> + * since our writepage() path may potentially allocate memory when
> + * calling into the lower fs vfs_write() which may in turn invoke
> + * us again.
> + */
> + if (current->flags & PF_MEMALLOC) {
> + redirty_page_for_writepage(wbc, page);
> + rc = 0;
> + goto out;
> + }
> +
> rc = ecryptfs_encrypt_page(page);
> if (rc) {
> ecryptfs_printk(KERN_WARNING, "Error encrypting "
> @@ -70,8 +82,8 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
> goto out;
> }
> SetPageUptodate(page);
> - unlock_page(page);
> out:
> + unlock_page(page);
> return rc;
> }
>
> @@ -486,6 +498,7 @@ static int ecryptfs_write_end(struct file *file,
> struct ecryptfs_crypt_stat *crypt_stat =
> &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
> int rc;
> + int need_unlock_page = 1;
>
> if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
> ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
> @@ -512,26 +525,26 @@ static int ecryptfs_write_end(struct file *file,
> "zeros in page with index = [0x%.16lx]\n", index);
> goto out;
> }
> - rc = ecryptfs_encrypt_page(page);
> - if (rc) {
> - ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
> - "index [0x%.16lx])\n", index);
> - goto out;
> - }
> + set_page_dirty(page);
> + unlock_page(page);
> + need_unlock_page = 0;
> if (pos + copied > i_size_read(ecryptfs_inode)) {
> i_size_write(ecryptfs_inode, pos + copied);
> ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
> "[0x%.16llx]\n",
> (unsigned long long)i_size_read(ecryptfs_inode));
> + balance_dirty_pages_ratelimited(mapping);
> + rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
> + if (rc) {
> + printk(KERN_ERR "Error writing inode size to metadata; "
> + "rc = [%d]\n", rc);
> + goto out;
> + }
> }
> - rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
> - if (rc)
> - printk(KERN_ERR "Error writing inode size to metadata; "
> - "rc = [%d]\n", rc);
> - else
> - rc = copied;
> + rc = copied;
> out:
> - unlock_page(page);
> + if (need_unlock_page)
> + unlock_page(page);
> page_cache_release(page);
> return rc;
> }
> diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c
> index db184ef..85d4309 100644
> --- a/fs/ecryptfs/read_write.c
> +++ b/fs/ecryptfs/read_write.c
> @@ -44,15 +44,11 @@ int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
> ssize_t rc;
>
> inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
> - mutex_lock(&inode_info->lower_file_mutex);
> BUG_ON(!inode_info->lower_file);
> - inode_info->lower_file->f_pos = offset;
> fs_save = get_fs();
> set_fs(get_ds());
> - rc = vfs_write(inode_info->lower_file, data, size,
> - &inode_info->lower_file->f_pos);
> + rc = vfs_write(inode_info->lower_file, data, size, &offset);
> set_fs(fs_save);
> - mutex_unlock(&inode_info->lower_file_mutex);
> mark_inode_dirty_sync(ecryptfs_inode);
> return rc;
> }
> @@ -234,15 +230,11 @@ int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
> mm_segment_t fs_save;
> ssize_t rc;
>
> - mutex_lock(&inode_info->lower_file_mutex);
> BUG_ON(!inode_info->lower_file);
> - inode_info->lower_file->f_pos = offset;
> fs_save = get_fs();
> set_fs(get_ds());
> - rc = vfs_read(inode_info->lower_file, data, size,
> - &inode_info->lower_file->f_pos);
> + rc = vfs_read(inode_info->lower_file, data, size, &offset);
> set_fs(fs_save);
> - mutex_unlock(&inode_info->lower_file_mutex);
> return rc;
> }
>
> diff --git a/fs/ecryptfs/super.c b/fs/ecryptfs/super.c
> index 3042fe1..e15ff06 100644
> --- a/fs/ecryptfs/super.c
> +++ b/fs/ecryptfs/super.c
> @@ -55,7 +55,6 @@ static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
> if (unlikely(!inode_info))
> goto out;
> ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
> - mutex_init(&inode_info->lower_file_mutex);
> inode_info->lower_file = NULL;
> inode = &inode_info->vfs_inode;
> out:
> @@ -198,7 +197,7 @@ static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
> const struct super_operations ecryptfs_sops = {
> .alloc_inode = ecryptfs_alloc_inode,
> .destroy_inode = ecryptfs_destroy_inode,
> - .drop_inode = generic_delete_inode,
> + .drop_inode = NULL,

For the sake of having one less NULL function pointer in the kernel, I
changed this from NULL to generic_drop_inode. :)

Tyler

> .statfs = ecryptfs_statfs,
> .remount_fs = NULL,
> .evict_inode = ecryptfs_evict_inode,
> --
> 1.7.3.1
>
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