direct-io: cleanup blockdev_direct_IO locking

Currently the locking in blockdev_direct_IO is a mess, we have three
different locking types and very confusing checks for some of them.  The
most complicated one is DIO_OWN_LOCKING for reads, which happens to not
actually be used.

This patch gets rid of the DIO_OWN_LOCKING - as mentioned above the read
case is unused anyway, and the write side is almost identical to
DIO_NO_LOCKING.  The difference is that DIO_NO_LOCKING always sets the
create argument for the get_blocks callback to zero, but we can easily
move that to the actual get_blocks callbacks.  There are four users of the
DIO_NO_LOCKING mode: gfs already ignores the create argument and thus is
fine with the new version, ocfs2 only errors out if create were ever set,
and we can remove this dead code now, the block device code only ever uses
create for an error message if we are fully beyond the device which can
never happen, and last but not least XFS will need the new behavour for
writes.

Now we can replace the lock_type variable with a flags one, where no flag
means the DIO_NO_LOCKING behaviour and DIO_LOCKING is kept as the first
flag.  Separate out the check for not allowing to fill holes into a
separate flag, although for now both flags always get set at the same
time.

Also revamp the documentation of the locking scheme to actually make
sense.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alex Elder <aelder@sgi.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 14 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index a057f48eb156..b23a7018eb90 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2264,9 +2264,11 @@ ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
         int lock_type);
 
 enum {
-        DIO_LOCKING = 1, /* need locking between buffered and direct access */
-        DIO_NO_LOCKING,  /* bdev; no locking at all between buffered/direct */
-        DIO_OWN_LOCKING, /* filesystem locks buffered and direct internally */
+        /* need locking between buffered and direct access */
+        DIO_LOCKING     = 0x01,
+
+        /* filesystem does not support filling holes */
+        DIO_SKIP_HOLES  = 0x02,
 };
 
 static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
@@ -2275,7 +2277,8 @@ static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
         dio_iodone_t end_io)
 {
         return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
-                                nr_segs, get_block, end_io, DIO_LOCKING);
+                                    nr_segs, get_block, end_io,
+                                    DIO_LOCKING | DIO_SKIP_HOLES);
 }
 
 static inline ssize_t blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
@@ -2284,16 +2287,7 @@ static inline ssize_t blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
         dio_iodone_t end_io)
 {
         return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
-                                nr_segs, get_block, end_io, DIO_NO_LOCKING);
-}
-
-static inline ssize_t blockdev_direct_IO_own_locking(int rw, struct kiocb *iocb,
-        struct inode *inode, struct block_device *bdev, const struct iovec *iov,
-        loff_t offset, unsigned long nr_segs, get_block_t get_block,
-        dio_iodone_t end_io)
-{
-        return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
-                                nr_segs, get_block, end_io, DIO_OWN_LOCKING);
+                                nr_segs, get_block, end_io, 0);
 }
 #endif