[PATCH 02/11] mm: call import_iovec() instead of rw_copy_check_uvector() in process_vm_rw()

Christoph Hellwig
2020-09-21T14:36:14Z

From: David Laight <David.Laight@ACULAB.COM>

This is the only direct call of rw_copy_check_uvector(). Removing it
will allow rw_copy_check_uvector() to be inlined into import_iovec(),
while only paying a minor price by setting up an otherwise unused
iov_iter in the process_vm_readv/process_vm_writev syscalls that aren't
in a super hot path.

Signed-off-by: David Laight <david.laight@aculab.com>
[hch: expanded the commit log, pass CHECK_IOVEC_ONLY instead of 0 for the
compat case, handle CHECK_IOVEC_ONLY in iov_iter_init]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
lib/iov_iter.c | 2 +-
mm/process_vm_access.c | 33 ++++++++++++++++++---------------
2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5e40786c8f1232..db54588406dfae 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -443,7 +443,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
const struct iovec *iov, unsigned long nr_segs,
size_t count)
{
- WARN_ON(direction & ~(READ | WRITE));
+ WARN_ON(direction & ~(READ | WRITE | CHECK_IOVEC_ONLY));
direction &= READ | WRITE;

/* It will get better. Eventually... */
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 29c052099affdc..40cd502c337534 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -264,7 +264,7 @@ static ssize_t process_vm_rw(pid_t pid,
struct iovec iovstack_r[UIO_FASTIOV];
struct iovec *iov_l = iovstack_l;
struct iovec *iov_r = iovstack_r;
- struct iov_iter iter;
+ struct iov_iter iter_l, iter_r;
ssize_t rc;
int dir = vm_write ? WRITE : READ;

@@ -272,23 +272,25 @@ static ssize_t process_vm_rw(pid_t pid,
return -EINVAL;

/* Check iovecs */
- rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
+ rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter_l);
if (rc < 0)
return rc;
- if (!iov_iter_count(&iter))
+ if (!iov_iter_count(&iter_l))
goto free_iovecs;

- rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
- iovstack_r, &iov_r);
+ rc = import_iovec(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, &iov_r,
+ &iter_r);
if (rc <= 0)
goto free_iovecs;

- rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
+ rc = process_vm_rw_core(pid, &iter_l, iter_r.iov, iter_r.nr_segs,
+ flags, vm_write);

free_iovecs:
if (iov_r != iovstack_r)
kfree(iov_r);
- kfree(iov_l);
+ if (iov_l != iovstack_l)
+ kfree(iov_l);

return rc;
}
@@ -322,30 +324,31 @@ compat_process_vm_rw(compat_pid_t pid,
struct iovec iovstack_r[UIO_FASTIOV];
struct iovec *iov_l = iovstack_l;
struct iovec *iov_r = iovstack_r;
- struct iov_iter iter;
+ struct iov_iter iter_l, iter_r;
ssize_t rc = -EFAULT;
int dir = vm_write ? WRITE : READ;

if (flags != 0)
return -EINVAL;

- rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
+ rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter_l);
if (rc < 0)
return rc;
- if (!iov_iter_count(&iter))
+ if (!iov_iter_count(&iter_l))
goto free_iovecs;
- rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
- UIO_FASTIOV, iovstack_r,
- &iov_r);
+ rc = compat_import_iovec(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
+ &iov_r, &iter_r);
if (rc <= 0)
goto free_iovecs;

- rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
+ rc = process_vm_rw_core(pid, &iter_l, iter_r.iov, iter_r.nr_segs,
+ flags, vm_write);

free_iovecs:
if (iov_r != iovstack_r)
kfree(iov_r);
- kfree(iov_l);
+ if (iov_l != iovstack_l)
+ kfree(iov_l);
return rc;
}

--
2.28.0