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Re: [PATCH 2/10] xfs: fix min bufsize bugs in two places

To: Alex Elder <aelder@xxxxxxx>
Subject: Re: [PATCH 2/10] xfs: fix min bufsize bugs in two places
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 13 Apr 2010 15:12:09 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20100412063248.GG2493@dastard>
References: <1270852013.7840.132.camel@doink> <20100412063248.GG2493@dastard>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Apr 12, 2010 at 04:32:48PM +1000, Dave Chinner wrote:
> On Fri, Apr 09, 2010 at 05:26:53PM -0500, Alex Elder wrote:
> > This fixes a bug in two places that I found by inspection.  In
> > xlog_find_verify_cycle() and xlog_write_log_records(), the code
> > attempts to allocate a buffer to hold as many blocks as possible.
> > It gives up if the number of blocks to be allocated gets too small.
> > Right now it uses log->l_sectbb_log as that lower bound, but I'm
> > sure it's supposed to be the actual log sector size instead.  That
> > is, the lower bound should be (1 << log->l_sectbb_log).
> > 
> > Also define a simple macro xlog_sectbb(log) to represent the number
> > of basic blocks in a sector for the given log.
> > 
> > (No change from original submission; I have implemented Christoph's
> > suggestion about storing l_sectsize rather than l_sectbb_log in
> > a new, separate patch in this series.)
> > 
> > Signed-off-by: Alex Elder <aelder@xxxxxxx>
> > 
> > ---
> > fs/xfs/xfs_log_recover.c |   21 +++++++++++++++++----
> >  fs/xfs/xfs_log_recover.c |   21 +++++++++++++++++----
> >  1 file changed, 17 insertions(+), 4 deletions(-)
> > 
> > Index: b/fs/xfs/xfs_log_recover.c
> > ===================================================================
> > --- a/fs/xfs/xfs_log_recover.c
> > +++ b/fs/xfs/xfs_log_recover.c
> > @@ -66,6 +66,9 @@ STATIC void       xlog_recover_check_summary(x
> >     ((bbs + (log)->l_sectbb_mask + 1) & ~(log)->l_sectbb_mask) : (bbs) )
> >  #define XLOG_SECTOR_ROUNDDOWN_BLKNO(log, bno)      ((bno) & 
> > ~(log)->l_sectbb_mask)
> >  
> > +/* Number of basic blocks in a log sector */
> > +#define xlog_sectbb(log) (1 << (log)->l_sectbb_log)
> > +
> 
> Can you do this without the #define? There's a spot in
> xlog_alloc_log() where the l_sectbb_mask is set up that
> open code this shift, so it seems to me that this woul dbe the spot
> to set up a l_sect_size variable and reference that instead...

I note you did this with a later patch, so this one is good to go.

Reviewed-by: Dave Chinner <david@xxxxxxxxxxxxx>

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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