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SubjectRe: [PATCH v2] eCryptfs: Write optimization for non-uptodate page
On 2012-02-05 23:33:51, Li Wang wrote:
> ecryptfs_write_begin() grabs a page from page cache for writing.
> If the page does not contain valid data, or the data are older than
> the counterpart on the disk, eCryptfs will read out the corresponding data
> from the disk into the eCryptfs page cache, decrypt them,
> then perform writing. However, for current page, if the length of
> the data to be written into is equal to page size, that means the whole
> page of data will be overwritten, in which case, it does not matter whatever
>
> the data were before, it is beneficial to perform writing directly.
>
> This is especially useful while using eCryptfs in backup situation, user
> copies file
> out from eCryptfs folder, modifies, and copies the revised file back to
> replace the original one.
>
> With this optimization, according to our test on a machine with IntelR Core
> T 2 Duo processor,
> iozone 'write' operation on an existing file with write size being multiple
> of page size will
> enjoy a steady 3x speedup.

Looks like your email client is incorrectly wrapping some lines.

>
> Signed-off-by: Li Wang <liwang@nudt.edu.cn>
> Signed-off-by: Yunchuan Wen <wenyunchuan@kylinos.com.cn>
> Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
>
> ---
>
> Changes from v1:
>
> The new version adds the code to handle short copy issue which may occure
> in iov_iter_copy_from_user_atomic(). The idea is to let ecryptfs_write_end()
> return zero,
> in order to give iov_iter_fault_in_readable() a chance to handle the page
> fault
> for the current iovec, then restart the copy operation.
>
> fs/ecryptfs/mmap.c | 12 ++++++++++--
> 1 files changed, 10 insertions(+), 2 deletions(-)
> diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
> index 10ec695..c6f665e 100644
> --- a/fs/ecryptfs/mmap.c
> +++ b/fs/ecryptfs/mmap.c
> @@ -350,7 +350,8 @@ static int ecryptfs_write_begin(struct file *file,
> if (prev_page_end_size
> >= i_size_read(page->mapping->host)) {
> zero_user(page, 0, PAGE_CACHE_SIZE);
> - } else {
> + SetPageUptodate(page);
> + } else if (len < PAGE_CACHE_SIZE) {
> rc = ecryptfs_decrypt_page(page);
> if (rc) {
> printk(KERN_ERR "%s: Error
> decrypting "

The patch didn't even apply because of this bad line wrap.

Looks like you've still got mail client issues, but I went ahead and
fixed everything up on my end. I just ask that you get these issues
straightened out soon. `git send-email` is a great way to send patches.
Give it a try.

I really appreciate you taking the time to fix up the commit message!

Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/tyhicks/ecryptfs.git#next

BTW, since this isn't a bug fix, it will live in -next until the 3.4
merge window.

Tyler

> @@ -360,8 +361,8 @@ static int ecryptfs_write_begin(struct file *file,
> ClearPageUptodate(page);
> goto out;
> }
> + SetPageUptodate(page);
> }
> - SetPageUptodate(page);
> }
> }
> /* If creating a page or more of holes, zero them out via truncate.
> @@ -512,6 +513,13 @@ static int ecryptfs_write_end(struct file *file,
> }
> goto out;
> }
> + if (!PageUptodate(page)) {
> + if (copied < PAGE_CACHE_SIZE) {
> + rc = 0;
> + goto out;
> + }
> + SetPageUptodate(page);
> + }
> /* Fills in zeros if 'to' goes beyond inode size */
> rc = fill_zeros_to_end_of_page(page, to);
> if (rc) {
>
> --
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