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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) {
    >
    > --
    > To unsubscribe from this list: send the line "unsubscribe ecryptfs" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
    [unhandled content-type:application/pgp-signature]
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