Messages in this thread | | | Date | Fri, 23 Nov 2012 03:19:39 -0500 | From | Christoph Hellwig <> | Subject | Re: [PATCH v4 09/31] dio: create a dio_aligned() helper function |
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On Wed, Nov 21, 2012 at 04:40:49PM -0600, Dave Kleikamp wrote: > From: Zach Brown <zab@zabbo.net> > > __blockdev_direct_IO() had two instances of the same code to determine > if a given offset wasn't aligned first to the inode's blkbits and then > to the underlying device's blkbits. This was confusing enough but > we're about to add code that performs the same check on offsets in bvec > arrays. Rather than add yet more copies of this code let's have > everyone call a helper. > > Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> > Cc: Zach Brown <zab@zabbo.net> > --- > fs/direct-io.c | 59 ++++++++++++++++++++++++++++++++++++---------------------- > 1 file changed, 37 insertions(+), 22 deletions(-) > > diff --git a/fs/direct-io.c b/fs/direct-io.c > index f86c720..035c0a3 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -1020,6 +1020,39 @@ static inline int drop_refcount(struct dio *dio) > } > > /* > + * Returns true if the given offset is aligned to either the IO size > + * specified by the given blkbits or by the logical block size of the > + * given block device. > + * > + * If the given offset isn't aligned to the blkbits arguments as this is > + * called then blkbits is set to the block size of the specified block > + * device. The call can then return either true or false. > + * > + * This bizarre calling convention matches the code paths that > + * duplicated the functionality that this helper was built from. We > + * reproduce the behaviour to avoid introducing subtle bugs. > + */ > +static int dio_aligned(unsigned long offset, unsigned *blkbits, > + struct block_device *bdev) > +{ > + unsigned mask = (1 << *blkbits) - 1; > + > + /* > + * Avoid references to bdev if not absolutely needed to give > + * the early prefetch in the caller enough time. > + */ > + > + if (offset & mask) { > + if (bdev) > + *blkbits = blksize_bits(bdev_logical_block_size(bdev));
I don't like having the blkbits assignment hidden in the helper, shouldn't we have a:
if (bdev) blkbits = blksize_bits(bdev_logical_block_size(bdev)); else blkbits = inode->i_blkbits;
in the caller instead?
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