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SubjectRe: [PATCH 8/11] eCryptfs: Convert mmap functions to use persistent file
On Mon, 17 Sep 2007 16:50:16 -0500 Michael Halcrow <mhalcrow@us.ibm.com> wrote:

> Convert readpage, prepare_write, and commit_write to use read_write.c
> routines. Remove sync_page; I cannot think of a good reason for
> implementing that in eCryptfs.
>
> Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
> ---
> fs/ecryptfs/mmap.c | 199 +++++++++++++++++++++++++++-------------------------
> 1 files changed, 103 insertions(+), 96 deletions(-)
>
> diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
> index 60e635e..dd68dd3 100644
> --- a/fs/ecryptfs/mmap.c
> +++ b/fs/ecryptfs/mmap.c
> @@ -267,9 +267,78 @@ static void set_header_info(char *page_virt,
> }
>
> /**
> + * ecryptfs_copy_up_encrypted_with_header
> + * @page: Sort of a ``virtual'' representation of the encrypted lower
> + * file. The actual lower file does not have the metadata in
> + * the header.
> + * @crypt_stat: The eCryptfs inode's cryptographic context
> + *
> + * The ``view'' is the version of the file that userspace winds up
> + * seeing, with the header information inserted.
> + */
> +static int
> +ecryptfs_copy_up_encrypted_with_header(struct page *page,
> + struct ecryptfs_crypt_stat *crypt_stat)
> +{
> + loff_t extent_num_in_page = 0;
> + loff_t num_extents_per_page = (PAGE_CACHE_SIZE
> + / crypt_stat->extent_size);
> + int rc = 0;
> +
> + while (extent_num_in_page < num_extents_per_page) {
> + loff_t view_extent_num = ((page->index * num_extents_per_page)

overflow?

> + + extent_num_in_page);
> +
> + if (view_extent_num < crypt_stat->num_header_extents_at_front) {
> + /* This is a header extent */
> + char *page_virt;
> +
> + page_virt = kmap_atomic(page, KM_USER0);
> + memset(page_virt, 0, PAGE_CACHE_SIZE);
> + /* TODO: Support more than one header extent */
> + if (view_extent_num == 0) {
> + rc = ecryptfs_read_xattr_region(
> + page_virt, page->mapping->host);
> + set_header_info(page_virt, crypt_stat);
> + }
> + kunmap_atomic(page_virt, KM_USER0);
> + flush_dcache_page(page);
> + if (rc) {
> + ClearPageUptodate(page);
> + printk(KERN_ERR "%s: Error reading xattr "
> + "region; rc = [%d]\n", __FUNCTION__, rc);
> + goto out;
> + }
> + SetPageUptodate(page);

I don't know what sort of page `page' refers to here, but normally we only
manipulate the page uptodate status under lock_page().


> + } else {
> + /* This is an encrypted data extent */
> + loff_t lower_offset =
> + ((view_extent_num -
> + crypt_stat->num_header_extents_at_front)
> + * crypt_stat->extent_size);

overflow?

> + rc = ecryptfs_read_lower_page_segment(
> + page, (lower_offset >> PAGE_CACHE_SHIFT),
> + (lower_offset & ~PAGE_CACHE_MASK),
> + crypt_stat->extent_size, page->mapping->host);
> + if (rc) {
> + printk(KERN_ERR "%s: Error attempting to read "
> + "extent at offset [%lld] in the lower "
> + "file; rc = [%d]\n", __FUNCTION__,
> + lower_offset, rc);
> + goto out;
> + }
> + }
> + extent_num_in_page++;
> + }
> +out:
> + return rc;
> +}
> +
> +/**
> * ecryptfs_readpage
> - * @file: This is an ecryptfs file
> - * @page: ecryptfs associated page to stick the read data into
> + * @file: An eCryptfs file
> + * @page: Page from eCryptfs inode mapping into which to stick the read data
> *
> * Read in a page, decrypting if necessary.
> *
> @@ -277,59 +346,35 @@ static void set_header_info(char *page_virt,
> */
> static int ecryptfs_readpage(struct file *file, struct page *page)
> {
> + struct ecryptfs_crypt_stat *crypt_stat =
> + &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
> int rc = 0;
> - struct ecryptfs_crypt_stat *crypt_stat;
>
> - BUG_ON(!(file && file->f_path.dentry && file->f_path.dentry->d_inode));
> - crypt_stat = &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)
> - ->crypt_stat;
> if (!crypt_stat
> || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
> || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
> ecryptfs_printk(KERN_DEBUG,
> "Passing through unencrypted page\n");
> - rc = ecryptfs_do_readpage(file, page, page->index);
> - if (rc) {
> - ecryptfs_printk(KERN_ERR, "Error reading page; rc = "
> - "[%d]\n", rc);
> - goto out;
> - }
> + rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
> + PAGE_CACHE_SIZE,
> + page->mapping->host);
> } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
> if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
> - int num_pages_in_header_region =
> - (crypt_stat->extent_size
> - / PAGE_CACHE_SIZE);
> -
> - if (page->index < num_pages_in_header_region) {
> - char *page_virt;
> -
> - page_virt = kmap_atomic(page, KM_USER0);
> - memset(page_virt, 0, PAGE_CACHE_SIZE);
> - if (page->index == 0) {
> - rc = ecryptfs_read_xattr_region(
> - page_virt, page->mapping->host);
> - set_header_info(page_virt, crypt_stat);
> - }
> - kunmap_atomic(page_virt, KM_USER0);
> - flush_dcache_page(page);
> - if (rc) {
> - printk(KERN_ERR "Error reading xattr "
> - "region\n");
> - goto out;
> - }
> - } else {
> - rc = ecryptfs_do_readpage(
> - file, page,
> - (page->index
> - - num_pages_in_header_region));
> - if (rc) {
> - printk(KERN_ERR "Error reading page; "
> - "rc = [%d]\n", rc);
> - goto out;
> - }
> + rc = ecryptfs_copy_up_encrypted_with_header(page,
> + crypt_stat);
> + if (rc) {
> + printk(KERN_ERR "%s: Error attempting to copy "
> + "the encrypted content from the lower "
> + "file whilst inserting the metadata "
> + "from the xattr into the header; rc = "
> + "[%d]\n", __FUNCTION__, rc);
> + goto out;
> }
> +
> } else {
> - rc = ecryptfs_do_readpage(file, page, page->index);
> + rc = ecryptfs_read_lower_page_segment(
> + page, page->index, 0, PAGE_CACHE_SIZE,
> + page->mapping->host);
> if (rc) {
> printk(KERN_ERR "Error reading page; rc = "
> "[%d]\n", rc);
> @@ -344,10 +389,7 @@ static int ecryptfs_readpage(struct file *file, struct page *page)
> goto out;
> }
> }
> - SetPageUptodate(page);
> out:
> - if (rc)
> - ClearPageUptodate(page);
> ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
> page->index);
> unlock_page(page);
> @@ -403,9 +445,12 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page,
> goto out; /* If we are writing a full page, it will be
> up to date. */
> if (!PageUptodate(page))
> - rc = ecryptfs_do_readpage(file, page, page->index);
> + rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
> + PAGE_CACHE_SIZE,
> + page->mapping->host);
> if (page->index != 0) {
> - loff_t end_of_prev_pg_pos = page_offset(page) - 1;
> + loff_t end_of_prev_pg_pos =
> + (((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);
>
> if (end_of_prev_pg_pos > i_size_read(page->mapping->host)) {
> rc = ecryptfs_truncate(file->f_path.dentry,
> @@ -633,18 +678,11 @@ static int ecryptfs_commit_write(struct file *file, struct page *page,
> unsigned from, unsigned to)
> {
> loff_t pos;
> - struct inode *inode;
> - struct inode *lower_inode;
> - struct file *lower_file;
> - struct ecryptfs_crypt_stat *crypt_stat;
> + struct inode *ecryptfs_inode = page->mapping->host;
> + struct ecryptfs_crypt_stat *crypt_stat =
> + &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
> int rc;
>
> - inode = page->mapping->host;
> - lower_inode = ecryptfs_inode_to_lower(inode);
> - lower_file = ecryptfs_file_to_lower(file);
> - mutex_lock(&lower_inode->i_mutex);
> - crypt_stat = &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)
> - ->crypt_stat;
> if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
> ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
> "crypt_stat at memory location [%p]\n", crypt_stat);
> @@ -654,6 +692,7 @@ static int ecryptfs_commit_write(struct file *file, struct page *page,
> ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
> "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
> to);
> + /* Fills in zeros if 'to' goes beyond inode size */
> rc = fill_zeros_to_end_of_page(page, to);
> if (rc) {
> ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
> @@ -667,25 +706,17 @@ static int ecryptfs_commit_write(struct file *file, struct page *page,
> "index [0x%.16x])\n", page->index);
> goto out;
> }
> - inode->i_blocks = lower_inode->i_blocks;
> - pos = page_offset(page) + to;
> - if (pos > i_size_read(inode)) {
> - i_size_write(inode, pos);
> + pos = (page->index << PAGE_CACHE_SHIFT) + to;

overflow

> + if (pos > i_size_read(ecryptfs_inode)) {
> + i_size_write(ecryptfs_inode, pos);
> ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
> - "[0x%.16x]\n", i_size_read(inode));
> + "[0x%.16x]\n", i_size_read(ecryptfs_inode));
> }
> - rc = ecryptfs_write_inode_size_to_metadata(inode);
> + rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
> if (rc)
> printk(KERN_ERR "Error writing inode size to metadata; "
> "rc = [%d]\n", rc);
> - lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
> - mark_inode_dirty_sync(inode);
> out:
> - if (rc < 0)
> - ClearPageUptodate(page);
> - else
> - SetPageUptodate(page);
> - mutex_unlock(&lower_inode->i_mutex);
> return rc;
> }
>
> @@ -751,34 +782,10 @@ static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
> return rc;
> }
>
> -static void ecryptfs_sync_page(struct page *page)
> -{
> - struct inode *inode;
> - struct inode *lower_inode;
> - struct page *lower_page;
> -
> - inode = page->mapping->host;
> - lower_inode = ecryptfs_inode_to_lower(inode);
> - /* NOTE: Recently swapped with grab_cache_page(), since
> - * sync_page() just makes sure that pending I/O gets done. */
> - lower_page = find_lock_page(lower_inode->i_mapping, page->index);
> - if (!lower_page) {
> - ecryptfs_printk(KERN_DEBUG, "find_lock_page failed\n");
> - return;
> - }
> - if (lower_page->mapping->a_ops->sync_page)
> - lower_page->mapping->a_ops->sync_page(lower_page);
> - ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
> - lower_page->index);
> - unlock_page(lower_page);
> - page_cache_release(lower_page);
> -}
> -
> struct address_space_operations ecryptfs_aops = {
> .writepage = ecryptfs_writepage,
> .readpage = ecryptfs_readpage,
> .prepare_write = ecryptfs_prepare_write,
> .commit_write = ecryptfs_commit_write,
> .bmap = ecryptfs_bmap,
> - .sync_page = ecryptfs_sync_page,
> };
> --
> 1.5.1.6
-
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