Julian Elischer wrote:
> Other than reading a few GB of data, is there a way to flush
> out the cache copy of a file I've written?
I don't know how this will fit into your application, but unmounting and
remounting the filesystem is a way that springs to mind. Perhaps not as
isloated as you'd lik
:When I get the time (probably not next week) I will write a patch
:to release the cached buffers that would prevent page removal.
I would appreciate a CC if/when you have something along these lines.
It won't be easy. The VM system has no reliable way to determine the
buffer cache bl
Julian Elischer wrote:
> with this bug could a user zero out /etc/group or similar?
> I am not sure what the ramification of the bug is..
The bug affects only in memory modified file data.
In memory modifications to the file can be deleted
and the file data reverts to a state before the
file mod
with this bug could a user zero out /etc/group or similar?
I am not sure what the ramification of the bug is..
On Fri, 23 Apr 2004, Stephan Uphoff wrote:
>
> Matthew Dillon wrote:
>
> >The idea with the fix is as follows:
> >
> >* It's hard to make the VM system invalidate buffers, s
Matthew Dillon wrote:
>The idea with the fix is as follows:
>
>* It's hard to make the VM system invalidate buffers, so don't try.
>
But it is easy to throw away clean buffers since they are nicely sorted
and easy to release.
Efficient locking is a bit tricky but should not be
On Thu, 22 Apr 2004, Matthew Dillon wrote:
> Sigh. Run this program. Note that the file contains an 'A' in the
> first byte after you run it (hexdump -C test.dat). Thus, msync()
> is not destroying the page until AFTER it finishes flushing it to
> disk.
>
> /*
> * x.c
> */
:(taking hackers off to reduce noise)
oops. I guess I didn't take it off hackers. Sorry about that.
Yah yah, I know, 'Matt's making a billion postings again'.
In anycase, I sent a patch set to Stephan and julian, and since I didn't
take it off the list like I said I would I gu
(taking hackers off to reduce noise)
I think all that needs to happen to fix this problem is to call
vm_object_page_remove() with the clean_only flag set to TRUE instead
of FALSE.
Wired pages, e.g. pages in the buffer cache, will not be removed, but
that's ok because memor
Ok... I've done some more testing.
Ahh! I finally was able to reproduce the problem with PROT_READ, and
I now see the code bit you were talking about. That's definitely a bug.
Here's the test program that reproduces the problem. This is definitely
a serious bug.
Sigh. Run this program. Note that the file contains an 'A' in the
first byte after you run it (hexdump -C test.dat). Thus, msync()
is not destroying the page until AFTER it finishes flushing it to
disk.
/*
* x.c
*/
#include
#include
#include
#include
#include
int
main(in
Matthew Dillon wrote:
> :Yes - but FreeBSD then calls vm_object_page_remove to remove the pages
> :from the vnode object. (vm_object_sync for 5.x or vm_map_clean for 4.x )
> < ... SNIP ...>
>
> I don't quite see that. Could you point out the code in question?
> (And, of course, a test p
:Yes - but FreeBSD then calls vm_object_page_remove to remove the pages
:from the vnode object. (vm_object_sync for 5.x or vm_map_clean for 4.x )
:
:Mhhh .. 4.X removes the pages without flushing if the file is not write
:mapped.
:This means that anyone with read access can screw up a file.
:(
Stephan Uphoff wrote:
> Matthew Dillon wrote:
> > :
> > :>
> > :> mmap() and msync(..MS_INVALIDATE..) should work.
> > :
> > :hmmm that is rather interesting..
> > :I wonder if it would work
> > :Maybe a vm guru could confirm this.. (under 4.x)
> > :
> >
> > Huh. If I hadn't looked at
Matthew Dillon wrote:
> :
> :>
> :> mmap() and msync(..MS_INVALIDATE..) should work.
> :
> :hmmm that is rather interesting..
> :I wonder if it would work
> :Maybe a vm guru could confirm this.. (under 4.x)
> :
>
> Huh. If I hadn't looked at the code I would have said that
> MS_INVA
:Actually what I'm looking for is
:"throw away clean data"
:
:I want to dump the cached version of a file so that I can force a reread
:of the disk.
MS_INVALIDATE doesn't do that.
madvise()'s MADV_FREE does what you want, BUT it does not currently
work (at least on 4.x or in DFly
On Wed, 21 Apr 2004, Matthew Dillon wrote:
> :
> :>
> :> mmap() and msync(..MS_INVALIDATE..) should work.
> :
> :hmmm that is rather interesting..
> :I wonder if it would work
> :Maybe a vm guru could confirm this.. (under 4.x)
> :
>
> Huh. If I hadn't looked at the code I would have
:
:>
:> mmap() and msync(..MS_INVALIDATE..) should work.
:
:hmmm that is rather interesting..
:I wonder if it would work
:Maybe a vm guru could confirm this.. (under 4.x)
:
Huh. If I hadn't looked at the code I would have said that
MS_INVALIDATE doesn't work in FreeBSD, but when I lo
On Wed, 21 Apr 2004, Stephan Uphoff wrote:
>
> mmap() and msync(..MS_INVALIDATE..) should work.
hmmm that is rather interesting..
I wonder if it would work
Maybe a vm guru could confirm this.. (under 4.x)
>
> Stephan
>
> >
> > Ok so I have an application where I need to
> > rere
mmap() and msync(..MS_INVALIDATE..) should work.
Stephan
>
> Ok so I have an application where I need to
> reread a file I have just written to ensure that it went to disk
> correctly..
>
> Other than reading a few GB of data, is there a way to flush
> out the cache copy of a file I'v
On Wed, Apr 21, 2004 at 01:47:43PM -0700, Julian Elischer wrote:
> ingenious, but, no we can't do that..
> As I mentionned.. someone suggested using 'dump'
> to extract the file from raw disk and checksumming that... :-)
If it is SCSI, you could probably put a second controler on the
SCSI bus, and
On Wed, 21 Apr 2004, Garance A Drosihn wrote:
> At 12:23 PM -0700 4/21/04, Julian Elischer wrote:
> >Ok so I have an application where I need to
> >reread a file I have just written to ensure that it went to disk
> >correctly..
> >
> >Other than reading a few GB of data, is there a way to flush
On Wed, 21 Apr 2004, Steve Watt wrote:
> On Apr 21, 13:28, Julian Elischer wrote:
> } Subject: Re: how to flush out cache.?
> }
> } On Wed, 21 Apr 2004, Steve Watt wrote:
> }
> } > In article <[EMAIL PROTECTED]> you write:
> } > >
> } > &g
On Wed, 21 Apr 2004, Steve Watt wrote:
> On Apr 21, 13:28, Julian Elischer wrote:
> } Subject: Re: how to flush out cache.?
> }
> } On Wed, 21 Apr 2004, Steve Watt wrote:
> }
> } > In article <[EMAIL PROTECTED]> you write:
> } > >
> } > &g
At 12:23 PM -0700 4/21/04, Julian Elischer wrote:
Ok so I have an application where I need to
reread a file I have just written to ensure that it went to disk
correctly..
Other than reading a few GB of data, is there a way to flush
out the cache copy of a file I've written?
possibilities include:
On Apr 21, 13:28, Julian Elischer wrote:
} Subject: Re: how to flush out cache.?
}
} On Wed, 21 Apr 2004, Steve Watt wrote:
}
} > In article <[EMAIL PROTECTED]> you write:
} > >
} > >Ok so I have an application where I need to
} > >reread a file I have just writte
On Wed, 21 Apr 2004, Julian Elischer wrote:
>
>
> On Wed, 21 Apr 2004, Steve Watt wrote:
>
> > In article <[EMAIL PROTECTED]> you write:
> > >
> > >Ok so I have an application where I need to
> > >reread a file I have just written to ensure that it went to disk
> > >correctly..
> > >
> > >Ot
On Wed, 21 Apr 2004, Steve Watt wrote:
> In article <[EMAIL PROTECTED]> you write:
> >
> >Ok so I have an application where I need to
> >reread a file I have just written to ensure that it went to disk
> >correctly..
> >
> >Other than reading a few GB of data, is there a way to flush
> >out the
In article <[EMAIL PROTECTED]> you write:
>
>Ok so I have an application where I need to
>reread a file I have just written to ensure that it went to disk
>correctly..
>
>Other than reading a few GB of data, is there a way to flush
>out the cache copy of a file I've written?
You can flush the fil
Ok so I have an application where I need to
reread a file I have just written to ensure that it went to disk
correctly..
Other than reading a few GB of data, is there a way to flush
out the cache copy of a file I've written?
possibilities include:
a file flag saying "don't keep a copy after it
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