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Message-ID: <20110503134636.GA6009@quack.suse.cz> Date: Tue, 3 May 2011 15:46:36 +0200 From: Jan Kara <jack@...e.cz> To: Surbhi Palande <surbhi.palande@...onical.com> Cc: jack@...e.cz, toshi.okajima@...fujitsu.com, tytso@....edu, m.mizuma@...fujitsu.com, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, sandeen@...hat.com Subject: Re: your mail On Tue 03-05-11 16:08:36, Surbhi Palande wrote: > On munmap() zap_pte_range() is called which dirties the PTE dirty pages as > Toshiyuki pointed out. > > zap_pte_range() > mapping->a_ops->set_page_dirty (= ext4_journalled_set_page_dirty) > > So, I think that it is here that we should do the checking for a ext4 F.S > frozen state and also prevent a parallel ext4 F.S freeze from happening. > > Attaching a patch for initial review. Please do let me know your thoughts! This is definitely the wrong place. ->set_page_dirty() callbacks are called with various locks held and the page need not be locked (thus dereferencing page->mapping is oopsable). Moreover this particular callback is called only in data=journal mode. Believe me, the right place is page_mkwrite() - you have to catch the read-only => read-write page transition. Once the page is mapped read-write, you've already lost the race. Honza -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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