> > Any suggestions or pointers would be greatly appreciated.
>
> Well, given the information you provided it is anyone's guess,
Yes, sorry about that :-) It's just nice to have a sanity check on the basic
principle - to check that I hadn't missed anything glaringly obvious... I do
have a strange feeling this isn't as hard as I'm finding it.
> 1) Check that you have a handler for the commit_write() address space
> operation.
Got that, and it's definitely being called.
> 2) Check that the handler marks the page as dirty by calling
> set_page_dirty(). Its variants like __set_page_dirty_buffers() and
> __set_page_dirty_nobuffers() may also be ok but since you are not
> block device based I don't think you should be using buffer_heads.
> Specifically SetPageDirty() is NOT enough because it does not mark
> the page dirty in the mapping tree (See
> documentation/filesystems/Locking for other details).
I've experimented with various versions of set_page_dirty(), and now have
settled back on the vanilla version.
I'd figured out that SetPageDirty() wasn't enough - eventually :-) Thanks for
noting it though.
> 3) If you have your own set_page_dirty() address space operation, make
> sure it does the right thing by eventually calling
> __set_page_dirty_nobuffers() (assuming you don't use buffer heads).
I'm not overriding set_page_dirty() anywhere (at the moment)
> 4) Check that writepages() does not kick in earlier and does not do
> the job instead.
I'm not implementing a writepages() method either, at the moment.
For more concrete discussion, here's a snippet of the code. This is my
current implementation of commit_write:
static int xenfs_commit_write(struct file *file, struct page *page, unsigned
from, unsigned to)
{
/* Some code taken from buffer.c::generic_commit_write */
struct inode *inode = page->mapping->host;
loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold i_mutex.
*/
if (pos > inode->i_size) {
i_size_write(inode, pos);
mark_inode_dirty(inode);
}
printk("xenfs_commit_write\n");
/* dumps out some data from the buffer so I can check it's correct. */
dumpbuf(page_address(page) + from, to - from);
printk("Setting page dirty!\n");
set_page_dirty(page);
printk("PageLocked = %d, PageUpToDate = %d, PageDirty = %d\n",
PageLocked(page), PageUptodate(page), PageDirty(page));
printk("Inode size = %lu", file->f_mapping->host->i_size);
/* Queue a writepage? */
return 0;
}
The first section of the code is just copied from the generic_commit_write()
function, comment included.
My printks here tell me:
PageLocked = 1, PageUpToDate = 1, PageDirty = 1
By the end of the function, as expected.
However, as far as I can tell, I don't get a call to my writepage() method at
any point after this, even if I run sync (although that does cause the
modified inode to get written out).
Am I doing something wrong in my commit_write() - where I've been assuming the
problem is - or should I be looking elsewhere?
Any help would be greatly appreciated!
Thanks very much,
Mark
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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