generic_file_aio_read() cleanups

As akpm points out, there's really no need for generic_file_aio_read to
make a special case of count 0: just loop through nr_segs doing nothing.
And as Harvey Harrison points out, there's no need to reset retval to 0
where it's already 0.

Setting count (or ocount) to 0 before calling generic_segment_checks is
unnecessary too; but reluctantly I'll leave that removal to someone with a
wider range of gcc versions to hand - 4.1.2 and 4.2.1 don't warn about it,
but perhaps others do - I forget which are the warniest versions.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Tested-by: Lawrence Greenfield <leg@google.com>
Cc: Christoph Rohland <hans-christoph.rohland@sap.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -1197,7 +1197,6 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 
 		mapping = filp->f_mapping;
 		inode = mapping->host;
-		retval = 0;
 		if (!count)
 			goto out; /* skip atime */
 		size = i_size_read(inode);
@@ -1209,15 +1208,13 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			}
 			if (retval > 0)
 				*ppos = pos + retval;
-		}
-		if (likely(retval != 0)) {
+			if (retval) {
 				file_accessed(filp);
 				goto out;
 			}
 		}
+	}
 
-	retval = 0;
-	if (count) {
 	for (seg = 0; seg < nr_segs; seg++) {
 		read_descriptor_t desc;
 
@@ -1227,7 +1224,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 		if (desc.count == 0)
 			continue;
 		desc.error = 0;
-			do_generic_file_read(filp,ppos,&desc,file_read_actor);
+		do_generic_file_read(filp, ppos, &desc, file_read_actor);
 		retval += desc.written;
 		if (desc.error) {
 			retval = retval ?: desc.error;
@@ -1236,7 +1233,6 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 		if (desc.count > 0)
 			break;
 	}
-	}
 out:
 	return retval;
 }