: 4/4GB: Ineffiecency in filemap.c

PATCH New Kirill Korotaev 1 participant 1 message Nov 11, 2004

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Memory management Page cache tmpfs (shmem filesystem)

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Kirill Korotaev

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2004-11-11 16:21 UTC #0 lore raw

PATCH 1/1 : 4/4GB: Ineffiecency in filemap.c

This patch fixes ineffiecency in copying user data in some code pieces
when 4GB split is ON:
filemap.c tries to call __copy_XXX_user while in atomic, but 4GB split
code always fails copying when in atomic. So this optimization for
normal kernels doesn't work with 4GB split, moreover, makes lot's of unnessaccary locks/checks.

Signed-off-by Kirill Korotaev <[email protected]>

Kirill

P.S. These 4GB split patches are against modified 2.6.8.1 kernel, but should be appliable to last Fedora kernels

mm/filemap.c renamed from mm/filemap.c.4gbcptusr +23 ~~-11~~

@@ -814,6 +814,7 @@ int file_read_actor(read_descriptor_t *d
 	if (size > count)
 		size = count;
 
+#ifndef CONFIG_X86_UACCESS_INDIRECT
 	/*
 	 * Faults on the destination of a read are common, so do it before
 	 * taking the kmap.

@@ -822,20 +823,23 @@ int file_read_actor(read_descriptor_t *d
 		kaddr = kmap_atomic(page, KM_USER0);
 		left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
 		kunmap_atomic(kaddr, KM_USER0);
-		if (left == 0)
-			goto success;
 	}
+#else
+	left = size;
+#endif
 
-	/* Do it the slow way */
-	kaddr = kmap(page);
-	left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
-	kunmap(page);
-
-	if (left) {
-		size -= left;
-		desc->error = -EFAULT;
+	if (left != 0) {
+		/* Do it the slow way */
+		kaddr = kmap(page);
+		left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
+		kunmap(page);
+
+		if (left) {
+			size -= left;
+			desc->error = -EFAULT;
+		}
 	}
-success:
+
 	desc->count = count - size;
 	desc->written += size;
 	desc->arg.buf += size;

@@ -1615,9 +1619,13 @@ filemap_copy_from_user(struct page *page
 	char *kaddr;
 	int left;
 
+#ifndef CONFIG_X86_UACCESS_INDIRECT
 	kaddr = kmap_atomic(page, KM_USER0);
 	left = __copy_from_user(kaddr + offset, buf, bytes);
 	kunmap_atomic(kaddr, KM_USER0);
+#else
+	left = bytes;
+#endif
 
 	if (left != 0) {
 		/* Do it the slow way */

@@ -1668,10 +1676,14 @@ filemap_copy_from_user_iovec(struct page
 	char *kaddr;
 	size_t copied;
 
+#ifndef CONFIG_X86_UACCESS_INDIRECT
 	kaddr = kmap_atomic(page, KM_USER0);
 	copied = __filemap_copy_from_user_iovec(kaddr + offset, iov,
 						base, bytes);
 	kunmap_atomic(kaddr, KM_USER0);
+#else
+	copied = 0;
+#endif
 	if (copied != bytes) {
 		kaddr = kmap(page);
 		copied = __filemap_copy_from_user_iovec(kaddr + offset, iov,

mm/shmem.c renamed from mm/shmem.c.4gbcptusr +2 -0

@@ -1322,6 +1322,7 @@ shmem_file_write(struct file *file, cons
 			break;
 
 		left = bytes;
+#ifndef CONFIG_X86_UACCESS_INDIRECT
 		if (PageHighMem(page)) {
 			volatile unsigned char dummy;
 			__get_user(dummy, buf);

@@ -1331,6 +1332,7 @@ shmem_file_write(struct file *file, cons
 			left = __copy_from_user(kaddr + offset, buf, bytes);
 			kunmap_atomic(kaddr, KM_USER0);
 		}
+#endif
 		if (left) {
 			kaddr = kmap(page);
 			left = __copy_from_user(kaddr + offset, buf, bytes);