Messages in this thread | | | Date | Tue, 13 Feb 2007 20:07:44 -0600 | From | "Eric Van Hensbergen" <> | Subject | Re: [RESEND][PATCH] 9p: add write-cache support to loose cache mode |
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On 2/13/07, Andrew Morton <akpm@linux-foundation.org> wrote: > > On Tue, 13 Feb 2007 17:55:31 -0600 Eric Van Hensbergen <ericvh@gmail.com> wrote: > > +int v9fs_prepare_write(struct file *file, struct page *page, > > + unsigned from, unsigned to) > > +{ > > + if (!PageUptodate(page)) { > > + if (to - from != PAGE_CACHE_SIZE) { > > + void *kaddr = kmap_atomic(page, KM_USER0); > > + memset(kaddr, 0, from); > > + memset(kaddr + to, 0, PAGE_CACHE_SIZE - to); > > + flush_dcache_page(page); > > + kunmap_atomic(kaddr, KM_USER0); > > + } > > + SetPageUptodate(page); > > + } > > This will mark the page uptodate while the piece between `to' and `from' is > uninitialised. A concurrent pagefault can come in and permit a read of > that uninitialised data. Because filemap_nopage() doesn't lock the page if > it is uptodate. >
Okay - I snagged this code from fs/libfs.c (simple_prepare_write) -- is that code also not correct, or am I just using it in the wrong context?
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