linux-ext4 - Re: [PATCH] ext3/4: Clear pagep after write

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Date:	Tue, 24 Feb 2009 13:11:33 +0300
From:	Dmitri Monakhov <dmonakhov@...nvz.org>
To:	Theodore Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext3/4: Clear pagep after write_begin() has failed

Theodore Tso <tytso@....edu> writes:

> On Tue, Feb 17, 2009 at 10:24:19PM +0300, Dmitri Monakhov wrote:
>> Seems there is no strict rule to for this case. In fact everybody
>> just ignored this variable after write_begin() has failed.
>> This was true until ext4_defrag_partial(). So let's follows simple
>> rule similar to block_write_begin().
>
> I've checked the latest ext4_defrag_partial, and it doesn't reference
> the page variable if write_begin() failed....
>
> 						- Ted
Latest posted defrag version 1.0 from 30 Jan, contains following code
+	up_write(&EXT4_I(org_inode)->i_data_sem);
+	ret = a_ops->write_begin(o_filp, mapping, offs, data_len, w_flags,
+								&page, &fsdata);
+	down_write(&EXT4_I(org_inode)->i_data_sem);
+
+	if (unlikely(ret < 0))
+		goto out;
.....
+out:
+	if (unlikely(page)) {
+		if (PageLocked(page))
+			unlock_page(page);
+		page_cache_release(page);
+	}
In fact the patch i'm propose is mostly a cleanup, rather then serious fix
for real issue. IMHO it is not bad idea to fold it in to some real patch.
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