On Fri, 5 Nov 2010 11:29:34 +0300
Pavel Shilovsky <piastryyy@xxxxxxxxx> wrote:
> On strict cache mode if we don't have Exclusive oplock we write a data to
> the server through cifs_user_write. Then if we Level II oplock store it in
> the cache, otherwise - invalidate inode pages affected by this writing.
>
> Signed-off-by: Pavel Shilovsky <piastryyy@xxxxxxxxx>
> ---
> fs/cifs/cifsfs.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++-----
> fs/cifs/file.c | 14 ++++++++++++--
> 2 files changed, 58 insertions(+), 7 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index bb7f36e..fbcd219 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -596,12 +596,53 @@ static ssize_t cifs_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
> static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> unsigned long nr_segs, loff_t pos)
> {
> - struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
> - ssize_t written;
> + struct inode *inode;
> + struct cifs_sb_info *cifs_sb;
> + ssize_t written, cache_written;
> + loff_t saved_pos;
> +
> + inode = iocb->ki_filp->f_path.dentry->d_inode;
> +
> + if (CIFS_I(inode)->clientCanCacheAll)
> + return generic_file_aio_write(iocb, iov, nr_segs, pos);
> +
> + cifs_sb = CIFS_SB(iocb->ki_filp->f_path.dentry->d_sb);
> +
> + if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO) == 0) {
> + int rc;
> +
> + written = generic_file_aio_write(iocb, iov, nr_segs, pos);
> +
> + rc = filemap_fdatawrite(inode->i_mapping);
> + if (rc)
> + cFYI(1, "cifs_file_aio_write: %d rc on %p inode",
> + rc, inode);
> + return written;
> + }
> +
> + saved_pos = pos;
> + written = cifs_user_write(iocb->ki_filp, iov->iov_base,
> + iov->iov_len, &pos);
> +
> + if (written > 0 && CIFS_I(inode)->clientCanCacheRead) {
> + /* we have data written to the server and at least oplock
> + for reading - store the date in the cache */
> + cache_written = generic_file_aio_write(iocb, iov,
> + nr_segs, saved_pos);
> + if (cache_written != written)
> + cERROR(1, "Cache written and server written data "
> + "lengths are different");
> + return written;
> + }
> +
> + if (written > 0)
> + invalidate_mapping_pages(inode->i_mapping,
> + saved_pos >> PAGE_CACHE_SHIFT,
> + (saved_pos+iov->iov_len-1)
> + >> PAGE_CACHE_SHIFT);
> +
> + iocb->ki_pos = pos;
>
> - written = generic_file_aio_write(iocb, iov, nr_segs, pos);
> - if (!CIFS_I(inode)->clientCanCacheAll)
> - filemap_fdatawrite(inode->i_mapping);
> return written;
> }
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index b36de2e..85824c0 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -1537,7 +1537,11 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
> struct page *page, void *fsdata)
> {
> int rc;
> - struct inode *inode = mapping->host;
> + struct inode *inode;
> + struct cifs_sb_info *cifs_sb;
> +
> + inode = mapping->host;
> + cifs_sb = CIFS_SB(inode->i_sb);
>
> cFYI(1, "write_end for page %p from pos %lld with %d bytes",
> page, pos, copied);
> @@ -1570,7 +1574,13 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
> } else {
> rc = copied;
> pos += copied;
> - set_page_dirty(page);
> + /* if we have strict cache switched on and don't have Exclusive
> + oplock for the inode, we don't have to set_page_dirty
> + because we flushed the data to the server in
> + cifs_file_aio_write before */
> + if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO) == 0 ||
> + CIFS_I(inode)->clientCanCacheAll)
> + set_page_dirty(page);
Is there a potential for a race here? Suppose I have clientCanCacheAll
set, I write to the cache, but before I get to cifs_write_end, an
oplock break is processed and clientCanCacheAll is cleared. Now I have
dirty data in cache but the dirty flag doesn't get set. Does anything
prevent that?
> }
>
> if (rc > 0) {
--
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