2010/11/29 Jeff Layton <jlayton@xxxxxxxxxx>:
> On Mon, 29 Nov 2010 13:58:05 +0300
> Pavel Shilovsky <piastryyy@xxxxxxxxx> wrote:
>
>> 2010/11/28 Jeff Layton <jlayton@xxxxxxxxxx>:
>> > On Sun, 28 Nov 2010 06:36:04 -0500
>> > Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>> >
>> >> On Sun, 28 Nov 2010 11:12:49 +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 | 40 ++++++++++++++++++++++++++++++++++++----
>> >> > 1 files changed, 36 insertions(+), 4 deletions(-)
>> >> >
>> >> > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
>> >> > index bbb5294..901c82b 100644
>> >> > --- a/fs/cifs/cifsfs.c
>> >> > +++ b/fs/cifs/cifsfs.c
>> >> > @@ -598,12 +598,44 @@ 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;
>> >> > + struct inode *inode;
>> >> > + struct cifs_sb_info *cifs_sb;
>> >> > ssize_t written;
>> >> >
>> >> > - written = generic_file_aio_write(iocb, iov, nr_segs, pos);
>> >> > - if (!CIFS_I(inode)->clientCanCacheAll)
>> >> > - filemap_fdatawrite(inode->i_mapping);
>> >> > + 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;
>> >> > + }
>> >> > +
>> >> > + /* in strict cache mode we need to write the data to the server exactly
>> >> > + from the pos to pos+len-1 rather than flush all affected pages
>> >> > + because it may cause a error with mandatory locks on these pages but
>> >> > + not on the region from pos to ppos+len-1 */
>> >>
>> >> Again, please fix the comment style. Here: ^^^^
>> >>
>> >> > + written = cifs_user_write(iocb->ki_filp, iov->iov_base,
>> >> > + iov->iov_len, &pos);
>> >> > +
>> >> > + iocb->ki_pos = pos;
>> >> > +
>> >> > + /* if we were successful - invalidate inode pages the write affected */
>> >> > + if (written > 0)
>> >> > + invalidate_mapping_pages(inode->i_mapping,
>> >> > + (pos-written) >> PAGE_CACHE_SHIFT,
>> >> > + (pos-1) >> PAGE_CACHE_SHIFT);
>> >> > +
>> >> > return written;
>> >> > }
>> >> >
>> >>
>> >> May god have mercy on anyone who tries to mix strictcache and mmap.
>> >>
>> >> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
>> >
>> > (cc'ing Suresh so he can comment)
>> >
>> > Actually...I'm going to withdraw my Reviewed-by tag here for now. This
>> > bare invalidate_mapping_pages doesn't deal with fscache.
>> >
>> > I think I need to understand what's intended when someone specifies
>> > strictcache and fsc before I can ack this. The simple answer would be
>> > that they are mutually exclusive, but if that's the case then the patch
>> > that adds the mount option needs to deal with that appropriately.
>>
>>
>> I don't think they can live together. I think we should do smth like a
>> following in mount options parsing:
>>
>> ...
>> if (opt == fscache) {
>> vol->fscahe = 1;
>> vol->strictcache = 0;
>> }
>> ...
>> if (opt == strictcache) {
>> vol->strictcache = 1;
>> vol->fscache = 0;
>> }
>>
>> So, if user specify both only the last will affect the client
>> behavior. Also we should add this information into cifs manpage.
>> Thoughts?
>>
>
> That would one way to deal with it.
>
> On the other hand though...fscache allows you to keep more data cached
> than you have RAM. This could be useful in a strictcache situation as
> well. Consider the case of an application on a client that has a lot of
> large files open for read. The server may grant oplocks on all of them.
> fscache would allow for fewer round trips to the server in such a case.
>
> So, another way to deal with it would be to simply invalidate the
> fscache whenever you'd invalidate the in-ram cache. I'm not sure what
> to do for the cifs_file_aio_write case where you're invalidating just a
> small range however.
>
According to the idea that we can't keep read oplock and writing to
the server in the same time, I think we can simply call
cifs_invalidate_mapping or even set invalidate_mapping flag on inode.
--
Best regards,
Pavel Shilovsky.
--
To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
