2012/11/27 Jeff Layton <jlayton@xxxxxxxxxx>:
> On Tue, 27 Nov 2012 10:50:28 +0400
> Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
>
>> If we have a read oplock and set a read lock in it, we can't write to the
>> locked area - so, filemap_fdatawrite may fail with a no information for a
>> userspace application even if we request a write to non-locked area. Fix
>> this by replacing it with filemap_write_and_wait call and sending non-page
>> write in a error case.
>>
>> While this may end up with two write requests to the server, we can be sure
>> that our data will be the same at the server and the page cache - the next read
>> on this file gets the valid data.
>>
>> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
>> ---
>> fs/cifs/file.c | 10 ++++------
>> 1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
>> index f8fe1bd..89efd85 100644
>> --- a/fs/cifs/file.c
>> +++ b/fs/cifs/file.c
>> @@ -2511,14 +2511,12 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
>> */
>> if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
>> ssize_t written;
>> - int rc;
>>
>> written = generic_file_aio_write(iocb, iov, nr_segs, pos);
>> - rc = filemap_fdatawrite(inode->i_mapping);
>> - if (rc)
>> - return (ssize_t)rc;
>> -
>> - return written;
>> + /* try page write at first */
>> + if (!filemap_write_and_wait(inode->i_mapping))
>> + return written;
>> + /* page write failed - try from pos to pos+len-1 */
>> }
>> #endif
>>
>
> Bleh -- nasty. I guess this will work though...
>
> Wonder if there's some way to populate the cache and then just mark the
> pages clean without sending out writes? That would be a better solution
> IMO, but I guess we can live with this for now...
>
> Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
Thanks for reviewing the patchset.
As for this patch I have the followon patch:
http://git.altlinux.org/people/piastry/public/?p=cifs-2.6.git;a=commitdiff;h=11673376e6840c686f0c6e51892b16ad1945887e
that allows us to populate the page cache without making pages dirty.
I didn't have enough time to test it well (that's why I haven't posted
it yet) - going to do it tomorrow. But you are welcome to comment the
approach.
--
Best regards,
Pavel Shilovsky.
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