Write to XFS in VFS and page cache

[David Chow <davidchow@xxxxxxxxxxxxxxxx>]

Dear xfs people,

I am new to this list . I am a stackable file system developer which means we 
write file systems for file systems. When my fs runs with xfs, I notice I got 
zero data written to the target file. My write path as follows,

xfspage=read_cache_page(xfsmapping, index,(filler_t *) 
xfsmapping->a_ops->readpage);
wait_on_page(xfspage);
xfs_aops->prepare_write(xfsfile, xfspage, offset, to);
kmap(xfspage);
memcpy(page_address(xfspage),somedata, somelength);
xfs_aops->commit_write(xfsfile, xfspage, offset, to);

Both prepare_write and commit_write returns 0 . I did a quick glance on the xfs 
code and notice that it is using the generic_commit_write() facility . Since my 
fs works on most of the file systems which also used the generic_commit_write() 
(e.g. ext2) . I am running Linux kernel 2.4.23 with XFS latest split patches on 
the SGI web site. If you can point out the pointers on how the XFS write path 
for dirty pages works, I will be appreciated. Any help and comment are welcome. 
Thanks.

regards,
David Chow