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Commit 136221fc authored by Wu Fengguang's avatar Wu Fengguang Committed by Trond Myklebust
Browse files

nfs: remove redundant tests on reading new pages 



aops->readpages() and its NFS helper readpage_async_filler() will only
be called to do readahead I/O for newly allocated pages. So it's not
necessary to test for the always 0 dirty/uptodate page flags.

The removal of nfs_wb_page() call also fixes a readahead bug: the NFS
readahead has been synchronous since 2.6.23, because that call will
clear PG_readahead, which is the reminder for asynchronous readahead.

More background: the PG_readahead page flag is shared with PG_reclaim,
one for read path and the other for write path. clear_page_dirty_for_io()
unconditionally clears PG_readahead to prevent possible readahead residuals,
assuming itself to be always called in the write path. However, NFS is one
and the only exception in that it _always_ calls clear_page_dirty_for_io()
in the read path, i.e. for readpages()/readpage().

Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarWu Fengguang <wfg@linux.intel.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 3d44cc3e

fs/nfs/read.c

+0 −6
Original line number Diff line number Diff line
@@ -533,12 +533,6 @@ readpage_async_filler(void *data, struct page *page) 
	unsigned int len;

	int error;



	error = nfs_wb_page(inode, page);

	if (error)

		goto out_unlock;

	if (PageUptodate(page))

		goto out_unlock;



	len = nfs_page_length(page);

	if (len == 0)

		return nfs_return_empty_page(page);