From dca692880e887739a669f6c41a80ca68ce2b09fc Mon Sep 17 00:00:00 2001 From: Steve French Date: Mon, 11 Nov 2013 16:42:37 -0600 Subject: [PATCH] [CIFS] O_DIRECT opens should work on directio mounts Opens on current cifs/smb2/smb3 mounts with O_DIRECT flag fail even when caching is disabled on the mount. This was reported by those running SMB2 benchmarks who need to be able to pass O_DIRECT on many of their open calls to reduce caching effects, but would also be needed by other applications. When mounting with forcedirectio ("cache=none") cifs and smb2/smb3 do not go through the page cache and thus opens with O_DIRECT flag should work (when posix extensions are negotiated we even are able to send the flag to the server). This patch fixes that in a simple way. The 9P client has a similar situation (caching is often disabled) and takes the same approach to O_DIRECT support ie works if caching disabled, but if client caching enabled it fails with EINVAL. A followon idea for a future patch as Pavel noted, could be that files opened with O_DIRECT could cause us to change inode->i_fop on the fly from cifs_file_strict_ops to cifs_file_direct_ops which would allow us to support this on non-forcedirectio mounts (cache=strict and cache=loose) as well. Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French --- fs/cifs/file.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 7ddddf2e2504..5a5a87240fe2 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -3663,6 +3663,27 @@ void cifs_oplock_break(struct work_struct *work) } } +/* + * The presence of cifs_direct_io() in the address space ops vector + * allowes open() O_DIRECT flags which would have failed otherwise. + * + * In the non-cached mode (mount with cache=none), we shunt off direct read and write requests + * so this method should never be called. + * + * Direct IO is not yet supported in the cached mode. + */ +static ssize_t +cifs_direct_io(int rw, struct kiocb *iocb, const struct iovec *iov, + loff_t pos, unsigned long nr_segs) +{ + /* + * FIXME + * Eventually need to support direct IO for non forcedirectio mounts + */ + return -EINVAL; +} + + const struct address_space_operations cifs_addr_ops = { .readpage = cifs_readpage, .readpages = cifs_readpages, @@ -3672,6 +3693,7 @@ const struct address_space_operations cifs_addr_ops = { .write_end = cifs_write_end, .set_page_dirty = __set_page_dirty_nobuffers, .releasepage = cifs_release_page, + .direct_IO = cifs_direct_io, .invalidatepage = cifs_invalidate_page, .launder_page = cifs_launder_page, }; -- 2.11.0