Re: [RFC] FADV_REMOVE

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Sat, 2008-08-16 at 16:33 +0100, David Woodhouse wrote:
> Any particular reason why I shouldn't do this?

... and (something similar to) this...

diff --git a/include/linux/fadvise.h b/include/linux/fadvise.h
index e8e7471..344ab0e 100644
--- a/include/linux/fadvise.h
+++ b/include/linux/fadvise.h
@@ -18,4 +18,6 @@
 #define POSIX_FADV_NOREUSE	5 /* Data will be accessed once.  */
 #endif
 
+#define LINUX_FADV_REMOVE	16 /* Discard data permanently */
+
 #endif	/* FADVISE_H_INCLUDED */
diff --git a/mm/fadvise.c b/mm/fadvise.c
index 343cfdf..c2e1baf 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -57,6 +57,7 @@ asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 		case POSIX_FADV_WILLNEED:
 		case POSIX_FADV_NOREUSE:
 		case POSIX_FADV_DONTNEED:
+		case LINUX_FADV_REMOVE:
 			/* no bad return value, but ignore advice */
 			break;
 		default:
@@ -119,6 +120,29 @@ asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 			invalidate_mapping_pages(mapping, start_index,
 						end_index);
 		break;
+	case LINUX_FADV_REMOVE:
+		if (!(file->f_mode & FMODE_WRITE)) {
+                        ret = -EBADF;
+			goto out;
+		}
+		if ((offset & ~PAGE_MASK) || (len & ~PAGE_MASK)) {
+			/* truncate_inode_pages_range() can't cope */
+			ret = -EINVAL;
+			goto out;
+		}
+		if (endbyte == -1) {
+			/* FIXME: truncate to end */
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (!mapping->host || !mapping->host->i_op ||
+		    !mapping->host->i_op->truncate_range) {
+			ret = -EINVAL;
+			goto out;
+		}
+		vmtruncate_range(mapping->host, offset, endbyte);
+		break;
 	default:
 		ret = -EINVAL;
 	}

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@xxxxxxxxx                              Intel Corporation



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