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>

diff --git a/mm/filemap.c b/mm/filemap.c
index 6343f3c..7675b91 100644 (file)
--- a/mm/filemap.c
+++ b/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);
@@ -1209,33 +1208,30 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
                        }
                        if (retval > 0)
                                *ppos = pos + retval;
-               }
-               if (likely(retval != 0)) {
-                       file_accessed(filp);
-                       goto out;
+                       if (retval) {
+                               file_accessed(filp);
+                               goto out;
+                       }
                }
        }
 
-       retval = 0;
-       if (count) {
-               for (seg = 0; seg < nr_segs; seg++) {
-                       read_descriptor_t desc;
+       for (seg = 0; seg < nr_segs; seg++) {
+               read_descriptor_t desc;
 
-                       desc.written = 0;
-                       desc.arg.buf = iov[seg].iov_base;
-                       desc.count = iov[seg].iov_len;
-                       if (desc.count == 0)
-                               continue;
-                       desc.error = 0;
-                       do_generic_file_read(filp,ppos,&desc,file_read_actor);
-                       retval += desc.written;
-                       if (desc.error) {
-                               retval = retval ?: desc.error;
-                               break;
-                       }
-                       if (desc.count > 0)
-                               break;
+               desc.written = 0;
+               desc.arg.buf = iov[seg].iov_base;
+               desc.count = iov[seg].iov_len;
+               if (desc.count == 0)
+                       continue;
+               desc.error = 0;
+               do_generic_file_read(filp, ppos, &desc, file_read_actor);
+               retval += desc.written;
+               if (desc.error) {
+                       retval = retval ?: desc.error;
+                       break;
                }
+               if (desc.count > 0)
+                       break;
        }
 out:
        return retval;