cuse(3): Allow shared memory allocations up to, but excluding 2 GBytes.

Currently the cuse(3) mmap(2) offset is split into 128 banks of 16 Mbytes.
Allow cuse(3) to make allocations that span multiple banks at the expense
of any fragmentation issues that may arise. Typically mmap(2) buffers are
well below 16 Mbytes. This allows 8K video resolution to work using webcamd.

Reviewed by:	markj @
Differential Revision:	https://reviews.freebsd.org/D35830
MFC after:	1 week
Sponsored by:	NVIDIA Networking

1 files changed, 42 insertions, 49 deletions

diff --git a/lib/libcuse/cuse_lib.c b/lib/libcuse/cuse_lib.c
index d241ce1dc4ac..ec300add5903 100644
--- a/lib/libcuse/cuse_lib.c
+++ b/lib/libcuse/cuse_lib.c
@@ -145,7 +145,7 @@ cuse_vmoffset(void *_ptr)
 	unsigned long n;
 
 	CUSE_LOCK();
-	for (n = 0; n != CUSE_ALLOC_UNIT_MAX; n++) {
+	for (n = remainder = 0; n != CUSE_ALLOC_UNIT_MAX; n++) {
 		if (a_cuse[n].ptr == NULL)
 			continue;
 
@@ -153,20 +153,13 @@ cuse_vmoffset(void *_ptr)
 		ptr_max = a_cuse[n].ptr + a_cuse[n].size - 1;
 
 		if ((ptr >= ptr_min) && (ptr <= ptr_max)) {
-
-			CUSE_UNLOCK();
-
 			remainder = (ptr - ptr_min);
-
-			remainder -= remainder %
-			    (unsigned long)getpagesize();
-
-			return ((n * CUSE_ALLOC_BYTES_MAX) + remainder);
+			break;
 		}
 	}
 	CUSE_UNLOCK();
 
-	return (0x80000000UL);		/* failure */
+	return ((n << CUSE_ALLOC_UNIT_SHIFT) + remainder);
 }
 
 void   *
@@ -174,70 +167,70 @@ cuse_vmalloc(int size)
 {
 	struct cuse_alloc_info info;
 	unsigned long pgsize;
+	unsigned long x;
+	unsigned long m;
 	unsigned long n;
 	void *ptr;
 	int error;
 
-	if (f_cuse < 0)
+	/* some sanity checks */
+	if (f_cuse < 0 || size < 1 || (unsigned long)size > CUSE_ALLOC_BYTES_MAX)
 		return (NULL);
 
 	memset(&info, 0, sizeof(info));
 
-	if (size < 1)
-		return (NULL);
-
 	pgsize = getpagesize();
 	info.page_count = howmany(size, pgsize);
 
-	CUSE_LOCK();
-	for (n = 0; n != CUSE_ALLOC_UNIT_MAX; n++) {
+	/* compute how many units the allocation needs */
+	m = howmany(size, 1 << CUSE_ALLOC_UNIT_SHIFT);
+	if (m == 0 || m > CUSE_ALLOC_UNIT_MAX)
+		return (NULL);
 
-		if (a_cuse[n].ptr != NULL)
+	CUSE_LOCK();
+	for (n = 0; n <= CUSE_ALLOC_UNIT_MAX - m; ) {
+		if (a_cuse[n].size != 0) {
+			/* skip to next available unit, depending on allocation size */
+			n += howmany(a_cuse[n].size, 1 << CUSE_ALLOC_UNIT_SHIFT);
 			continue;
-
-		a_cuse[n].ptr = ((uint8_t *)1);	/* reserve */
-		a_cuse[n].size = 0;
-
+		}
+		/* check if there are "m" free units ahead */
+		for (x = 1; x != m; x++) {
+			if (a_cuse[n + x].size != 0)
+				break;
+		}
+		if (x != m) {
+			/* skip to next available unit, if any */
+			n += x + 1;
+			continue;
+		}
+		/* reserve this unit by setting the size to a non-zero value */
+		a_cuse[n].size = size;
 		CUSE_UNLOCK();
 
 		info.alloc_nr = n;
 
 		error = ioctl(f_cuse, CUSE_IOCTL_ALLOC_MEMORY, &info);
 
-		if (error) {
-
-			CUSE_LOCK();
-
-			a_cuse[n].ptr = NULL;
-
-			if (errno == EBUSY)
-				continue;
-			else
-				break;
-		}
-		ptr = mmap(NULL, info.page_count * pgsize,
-		    PROT_READ | PROT_WRITE,
-		    MAP_SHARED, f_cuse, CUSE_ALLOC_BYTES_MAX * n);
-
-		if (ptr == MAP_FAILED) {
+		if (error == 0) {
+			ptr = mmap(NULL, info.page_count * pgsize,
+			    PROT_READ | PROT_WRITE,
+			    MAP_SHARED, f_cuse, n << CUSE_ALLOC_UNIT_SHIFT);
 
-			error = ioctl(f_cuse, CUSE_IOCTL_FREE_MEMORY, &info);
+			if (ptr != MAP_FAILED) {
+				CUSE_LOCK();
+				a_cuse[n].ptr = ptr;
+				CUSE_UNLOCK();
 
-			if (error) {
-				/* ignore */
+				return (ptr);		/* success */
 			}
-			CUSE_LOCK();
 
-			a_cuse[n].ptr = NULL;
-
-			break;
+			(void) ioctl(f_cuse, CUSE_IOCTL_FREE_MEMORY, &info);
 		}
-		CUSE_LOCK();
-		a_cuse[n].ptr = ptr;
-		a_cuse[n].size = size;
-		CUSE_UNLOCK();
 
-		return (ptr);		/* success */
+		CUSE_LOCK();
+		a_cuse[n].size = 0;
+		n++;
 	}
 	CUSE_UNLOCK();
 	return (NULL);			/* failure */