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iov_iter: Separate type from direction and use accessor functions

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In the iov_iter struct, separate the iterator type from the iterator
direction and use accessor functions to access them in most places.

Convert a bunch of places to use switch-statements to access them rather
then chains of bitwise-AND statements.  This makes it easier to add further
iterator types.  Also, this can be more efficient as to implement a switch
of small contiguous integers, the compiler can use ~50% fewer compare
instructions than it has to use bitwise-and instructions.

Further, cease passing the iterator type into the iterator setup function.
The iterator function can set that itself.  Only the direction is required.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
2018-10-20 00:57:56 +01:00
parent 00e2370744
commit aa563d7bca
40 changed files with 96 additions and 105 deletions
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4
fs/nfsd/vfs.c
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@@ -923,7 +923,7 @@ __be32 nfsd_readv(struct svc_rqst *rqstp, struct svc_fh *fhp,
int host_err;
trace_nfsd_read_vector(rqstp, fhp, offset, *count);
iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
iov_iter_kvec(&iter, READ, vec, vlen, *count);
host_err = vfs_iter_read(file, &iter, &offset, 0);
return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
}
@@ -999,7 +999,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
if (stable && !use_wgather)
flags |= RWF_SYNC;
iov_iter_kvec(&iter, WRITE | ITER_KVEC, vec, vlen, *cnt);
iov_iter_kvec(&iter, WRITE, vec, vlen, *cnt);
host_err = vfs_iter_write(file, &iter, &pos, flags);
if (host_err < 0)
goto out_nfserr;