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Date: Thu, 04 Jan 2001 12:38:45 -0500
From: Chris Mason <mason@suse.com>
To: Rik van Riel <riel@conectiva.com.br>,
        Marcelo Tosatti <marcelo@conectiva.com.br>
cc: Christoph Rohland <cr@sap.com>, Linus Torvalds <torvalds@transmeta.com>,
        Alexander Viro <viro@math.psu.edu>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] filemap_fdatasync & related changes
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Ok, lets just fix filemap_fdatasync.  We can tackle the msync/fsync
interaction with screwed up FS writepages later, since all of the existing
writepage funcs are safe.  The problems I see with filemap_fdatasync when
writepage returns 1:

The page dirty bit is not reset.
the page is never unlocked.

So how about something like this in filemap_fdatasync

ret = writepage(page) ;
if (ret == 1) {
    /* writepage declined to write it out,
    ** leave it on the locked list, but make
    ** sure the dirty bit stays on so the page
    ** doesn't disappear
    */
    SetPageDirty(page) ;
    UnlockPage(page) ;
}

And then, in filemap_fdatawait:

list_del(&page->list) ;
if (PageDirty(page))
    list_add(&page->list, &mapping->dirty_pages) ;
else
    list_add(&page->list, &mapping->clean_pages) ;

-chris
-
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