linux-kernel - Re: [PATCH -mm 1/5][AIO] - Rework compat_sys_io

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Message-ID: <20061130164943.348185a2@frecb000686>
Date:	Thu, 30 Nov 2006 16:49:43 +0100
From:	Sébastien Dugué <sebastien.dugue@...l.net>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linux-aio <linux-aio@...ck.org>, Andrew Morton <akpm@...l.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Zach Brown <zach.brown@...cle.com>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Jean Pierre Dion <jean-pierre.dion@...l.net>,
	Bharata B Rao <bharata@...ibm.com>
Subject: Re: [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit


                 compat_sys_io_submit() cleanup


  Cleanup compat_sys_io_submit by duplicating some of the native syscall
logic in the compat layer and directly calling io_submit_one() instead
of fooling the syscall into thinking it is called from a native 64-bit
caller.

  This eliminates:

  - the overhead of copying the nr iocb pointers on the userspace stack

  - the PAGE_SIZE/(sizeof(void *)) limit on the number of iocbs that
    can be submitted.

  This is also needed for the completion notification patch to avoid having
to rewrite each iocb on the caller stack for io_submit_one() to find the
sigevents.


 compat.c |   61 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 34 insertions(+), 27 deletions(-)

Signed-off-by: Sébastien Dugué <sebastien.dugue@...l.net>

Index: linux-2.6.19-rc6-mm2/fs/compat.c
===================================================================
--- linux-2.6.19-rc6-mm2.orig/fs/compat.c	2006-11-30 10:00:18.000000000 +0100
+++ linux-2.6.19-rc6-mm2/fs/compat.c	2006-11-30 13:12:32.000000000 +0100
@@ -642,40 +642,47 @@ out:
 	return ret;
 }
 
-static inline long
-copy_iocb(long nr, u32 __user *ptr32, struct iocb __user * __user *ptr64)
-{
-	compat_uptr_t uptr;
-	int i;
-
-	for (i = 0; i < nr; ++i) {
-		if (get_user(uptr, ptr32 + i))
-			return -EFAULT;
-		if (put_user(compat_ptr(uptr), ptr64 + i))
-			return -EFAULT;
-	}
-	return 0;
-}
-
-#define MAX_AIO_SUBMITS 	(PAGE_SIZE/sizeof(struct iocb *))
-
 asmlinkage long
 compat_sys_io_submit(aio_context_t ctx_id, int nr, u32 __user *iocb)
 {
-	struct iocb __user * __user *iocb64; 
-	long ret;
+	struct kioctx *ctx;
+	long ret = 0;
+	int i;
 
 	if (unlikely(nr < 0))
 		return -EINVAL;
 
-	if (nr > MAX_AIO_SUBMITS)
-		nr = MAX_AIO_SUBMITS;
-	
-	iocb64 = compat_alloc_user_space(nr * sizeof(*iocb64));
-	ret = copy_iocb(nr, iocb, iocb64);
-	if (!ret)
-		ret = sys_io_submit(ctx_id, nr, iocb64);
-	return ret;
+	if (unlikely(!access_ok(VERIFY_READ, iocb, (nr * sizeof(u32)))))
+		return -EFAULT;
+
+	ctx = lookup_ioctx(ctx_id);
+	if (unlikely(!ctx))
+		return -EINVAL;
+
+	for (i=0; i<nr; i++) {
+		compat_uptr_t uptr;
+		struct iocb __user *user_iocb;
+		struct iocb tmp;
+
+		if (unlikely(get_user(uptr, iocb + i))) {
+			ret = -EFAULT;
+			break;
+		}
+
+		user_iocb = compat_ptr(uptr);
+
+		if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
+			ret = -EFAULT;
+			break;
+		}
+
+		ret = io_submit_one(ctx, user_iocb, &tmp);
+		if (ret)
+			break;
+	}
+
+	put_ioctx(ctx);
+	return i ? i: ret;
 }
 
 struct compat_ncp_mount_data {
-
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