From mboxrd@z Thu Jan  1 00:00:00 1970
From: Badari Pulavarty <pbadari@gmail.com>
Subject: Re: [ANNOUNCE] new new aops patchset
Date: Wed, 04 Apr 2007 16:05:19 -0700
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References: <20070402120934.GA19626@wotan.suse.de>
	 <20070404221034.GF21982@ca-server1.us.oracle.com>
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Cc: Nick Piggin <npiggin@suse.de>,
	Linux Filesystems <linux-fsdevel@vger.kernel.org>,
	Steven Whitehouse <swhiteho@redhat.com>
To: Mark Fasheh <mark.fasheh@oracle.com>
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On Wed, 2007-04-04 at 15:10 -0700, Mark Fasheh wrote:
...
> +int pagecache_write_begin(struct file *file, struct address_space *mapping,
> +				loff_t pos, unsigned len, unsigned flags,
> +				struct page **pagep, void **fsdata)
> +{
> +	const struct address_space_operations *aops = mapping->a_ops;
> +
> +	if (aops->write_begin) {
> +		return aops->write_begin(file, mapping, pos, len, flags,
> +							pagep, fsdata);
> +	} else {
> +		int ret;
> +		pgoff_t index = pos >> PAGE_CACHE_SHIFT;
> +		unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
> +		struct inode *inode = mapping->host;
> +		struct page *page;
> +again:
> +		page = __grab_cache_page(mapping, index);
> +		*pagep = page;
> +		if (!page)
> +			return -ENOMEM;
> +
> +		if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
> +			/*
> +			 * There is no way to resolve a short write situation
> +			 * for a !Uptodate page (except by double copying in
> +			 * the caller done by generic_perform_write_2copy).
> +			 *
> +			 * Instead, we have to bring it uptodate here.
> +			 */
> +			ret = aops->readpage(file, page);
> +			page_cache_release(page);
> +			if (ret) {
> +				if (ret == AOP_TRUNCATED_PAGE)
> +					goto again;
> +				return ret;
> +			}
> +			goto again;
> +		}
> +
> +		ret = aops->prepare_write(file, page, offset, offset+len);
> +		if (ret) {
> +			if (ret != AOP_TRUNCATED_PAGE)
> +				unlock_page(page);
> +			page_cache_release(page);
> +			if (pos + len > inode->i_size)
> +				vmtruncate(inode, inode->i_size);
> +			if (ret == AOP_TRUNCATED_PAGE)
> +				goto again;
> +		}
> +		return ret;
> +	}


Hmm.. Okay, only filesystems that could return AOP_TRUNCATED_PAGE
are ocf2 and gfs2. Now that both of them are switched to have
write_begin()/write_end(), why do we need this code to handle
AOP_TRUNCATED_PAGE (in the else part) ? Can't we just cleanup/nuke
all the AOP_TRUNCATED_PAGE handling ?

Dumb question ?

Thanks,
Badari