[U-Boot] [PATCH v2] ext2: Cache line aligned partial sector bounce buffer

[Mike Frysinger]

On Monday, August 22, 2011 17:48:47 Anton Staaf wrote:
> On Mon, Aug 22, 2011 at 2:42 PM, Wolfgang Denk wrote:
> > Anton Staaf wrote:
> >> Currently, if a device read request is done that does not begin or end
> >> on a sector boundary a stack allocated bounce buffer is used to perform
> >> the read, and then just the part of the sector that is needed is copied
> >> into the users buffer.  This stack allocation can mean that the bounce
> >> buffer will not be aligned to the dcache line size.  This is a problem
> >> when caches are enabled because unaligned cache invalidates are not
> >> safe.
> >> 
> >> This patch allocates a cache line size aligned sector sized bounce
> >> buffer the first time that ext2fs_devread is called.
> > 
> > ...and never frees ist, which is a bad thing.  Please fix.
> 
> That was actually intentional.  To free the buffer the code would need
> to know when it was done doing ext2 accesses.  This information isn't
> really available.  And it would be a performance hit to allocate and
> free the buffer every time a read was performed, instead this patch
> re-uses the same allocated buffer every time that the read is called.
> Would you prefer that I allocate and free the buffer each time?  I can
> see an argument for that since it would mean that the code could also
> be called from multiple threads simultaneously, not that we have any
> such thing to worry about at the moment.

i'm not sure i follow ... the current code always frees it upon func exit.  
why cant yours do the same ?
-mike
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