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Message-ID: <20080123202045.GF23304@atrey.karlin.mff.cuni.cz> Date: Wed, 23 Jan 2008 21:20:45 +0100 From: Jan Kara <jack@...e.cz> To: Abhishek Rai <abhishekrai@...gle.com> Cc: linux-ext4@...r.kernel.org Subject: Re: Confused by journaling code in ext3_new_blocks() Hello, > I have the following question related to the journaling code in > ext3_new_blocks() function of fs/ext3/balloc.c, any help in this > regard will be greatly appreciated. The code snippet below is taken > from 2.6.24-rc8-mm1 but this code has changed little for a long time > so it's likely that any other recent kernel will also have very > similar code. > > ext3_new_blocks() > -> ext3_try_to_allocate_with_rsv() > -> ext3_journal_dirty_metadata(handle, bitmap_bh) > ... > allocated: > if ( /*sanity checking of newly allocated block numbers*/) { > ext3_error(...); > goto out; > } > > out: > ... > brelse(bitmap_bh); > return 0; > > > In the above code snippet, ext3_try_to_allocate_with_rsv() is marking > bitmap_bh as dirty metadata _before_ the sanity checks. I'm not > worried about the sanity checks as such, but it seems to me that if > the checks were to fail, we'd be committing the bitmap_bh updates to > disk even though it violates metadata sanity, or am I missing > something here ? Actually, it depends. Because if sanity checks fail, we call ext3_error() which remounts fs R/O or panics in most cases. Only if errors=continue is set, we really get to committing the wrong bitmap data. But I don't think this really is a problem - fsck has to be run anyway and it rebuilds the bitmaps from scratch. Honza -- Jan Kara <jack@...e.cz> SuSE CR Labs - 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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