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SubjectRe: [PATCH] ecryptfs: modify write path to encrypt page in writepage
On Thu Feb 24, 2011 at 01:17:51PM -0800, Thieu Le <thieule@chromium.org> wrote:
> Hi Tyler,
>
> Sorry for the delay, got sidetracked with some other work. I've addressed the
> dd hang and the low memory condition as discussed in IRC.
>
> PTAL.
>
> Thanks,
> Thieu

Hey Thieu - Not a problem.

I'll need a proper commit message and signed-off-by line before I can
commit this.

>
> ---
> fs/ecryptfs/ecryptfs_kernel.h | 1 -
> fs/ecryptfs/file.c | 9 +++++++-
> fs/ecryptfs/main.c | 2 -
> fs/ecryptfs/mmap.c | 46 ++++++++++++++++++++++++++++------------
> fs/ecryptfs/read_write.c | 12 +---------
> fs/ecryptfs/super.c | 1 -
> 6 files changed, 42 insertions(+), 29 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..d375210 100644
> --- a/fs/ecryptfs/mmap.c
> +++ b/fs/ecryptfs/mmap.c
> @@ -62,6 +62,23 @@ 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.
> + *
> + * This avoids stack overflows when called from deeply used stacks in
> + * random callers for direct reclaim or memcg reclaim. We explicitly
> + * allow reclaim from kswapd as the stack usage there is relatively low.

Stack size is a problem with eCryptfs, but we also have the issue of
potential memory allocations in our writepage() path due to calling
vfs_write() on the lower file. I don't think we can allow reclaim from
kswapd.

> + *
> + * This should really be done by the core VM, but until that happens
> + * filesystems like XFS, btrfs and ext4 have to take care of this
> + * by themselves.
> + */

Please make this entire comment block specific to eCryptfs instead of
something copied from XFS.

> + if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == 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 +87,8 @@ 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 +503,7 @@ 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 +530,26 @@ 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..15c969e 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:
> --
> 1.7.3.1
>


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