Re: [Fwd: [PATCH] consolidate generic_writepages and mpage_writepages]

[Miklos Szeredi]

> >Maybe cifs_writepages() too can use this infrastructure, but I'm not
> >touching that with a ten-foot pole.
> >  
> >
> The cifs case ought to be one of the simpler ones, pseudo-code is pretty 
> easy, the hard part is all of the stuff unrelated to cifs:
> Ideally if there were generic functions to help out, cifs writepages 
> would look roughly like the following
> 
> cifs_writepages(struct address_space *mapping, struct writeback_control 
> *wbc)
> {
>
> while (no more pages to write) {
> /* find writeable file handle for this inode */
> /* find the biggest set of contiguous pages that total less than 
> wsize */
> if (packet signing is enabled)
> /* write lock pages so they can not be changed under us 
> while we are calculating the checksum */
>   
>CIFSSMBWrite2(tree_connection, network_file_handle, array of 
> iovecs, number of iovecs);
> 
> if(packet signing was enabled)
> /* unlock pages */
> 
> if(error) {
>  set page errors
>  if (mounted "hard" )
>continue; /* retry */
>  else /* if no retry possible */
>return error to caller;
>}
> update bytes written statistics
> update index to point to next set of pages
> }  /* end while loop */
> }

write_cache_pages() now takes care of the 

 while (no more pages to write) {
 }

part.  All you have to do is to make the body of the loop into a
function and pass it a structure with the data you want to preserve
between invocations.

The hard part is untangling the breaks and continues.

Miklos
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Re: [Fwd: [PATCH] consolidate generic_writepages and mpage_writepages]

[Steve French (smfltc)]

From: Miklos Szeredi <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] consolidate generic_writepages and mpage_writepages
Date:   Fri, 16 Feb 2007 17:23:25 +0100

From: Miklos Szeredi <[EMAIL PROTECTED]>

Clean up massive code duplication between mpage_writepages() and
generic_writepages().

The new generic function, write_cache_pages() takes a function pointer
argument, which will be called for each page to be written.

Maybe cifs_writepages() too can use this infrastructure, but I'm not
touching that with a ten-foot pole.
 

The cifs case ought to be one of the simpler ones, pseudo-code is pretty 
easy, the hard part is all of the stuff unrelated to cifs:
Ideally if there were generic functions to help out, cifs writepages 
would look roughly like the following


cifs_writepages(struct address_space *mapping, struct writeback_control 
*wbc)

{
  
   while (no more pages to write) {

   /* find writeable file handle for this inode */
   /* find the biggest set of contiguous pages that total less than 
wsize */

   if (packet signing is enabled)
   /* write lock pages so they can not be changed under us 
while we are calculating the checksum */
 
  CIFSSMBWrite2(tree_connection, network_file_handle, array of 
iovecs, number of iovecs);


   if(packet signing was enabled)
   /* unlock pages */

   if(error) {
set page errors
if (mounted "hard" )
  continue; /* retry */
else /* if no retry possible */
  return error to caller;
  }
   update bytes written statistics
   update index to point to next set of pages
   }  /* end while loop */
}


If it were even better, CIFSSMBWrite2 could be called async - so that it 
did not have to wait for a network response from Samba (just an ack from 
TCP), before issuing the next write onto the wire - but this would 
require that we could queue a pointer to a completion routine to the mpx 
entry.

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