From 7ed529dab9572f54b50df10486b91b4eb34409ed Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@redhat.com>
Date: Mon, 18 Jul 2011 13:21:35 -0400
Subject: [PATCH] --- yaml --- r: 257392 b: refs/heads/master c:
 982d816581eeeacfe5b2b7c6d47d13a157616eff h: refs/heads/master v: v3

---
 [refs]                                  |  2 +-
 trunk/Documentation/filesystems/porting | 10 ++++++
 trunk/fs/read_write.c                   | 44 +++++++++++++++++++++++--
 trunk/include/linux/fs.h                |  4 ++-
 4 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index 73ec75970a10..990dccbc11b9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b4d5b10fb2e3a4327838c07d8ebd9e350fcc133d
+refs/heads/master: 982d816581eeeacfe5b2b7c6d47d13a157616eff
diff --git a/trunk/Documentation/filesystems/porting b/trunk/Documentation/filesystems/porting
index 0eeb3954dea3..6b96773e27cb 100644
--- a/trunk/Documentation/filesystems/porting
+++ b/trunk/Documentation/filesystems/porting
@@ -411,3 +411,13 @@ to some pointer to returning that pointer.  On errors return ERR_PTR(...).
 argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask.
 	generic_permission() has also lost the check_acl argument; if you want
 non-NULL to be used for that inode, put it into ->i_op->check_acl.
+
+--
+[mandatory]
+	If you implement your own ->llseek() you must handle SEEK_HOLE and
+SEEK_DATA.  You can hanle this by returning -EINVAL, but it would be nicer to
+support it in some way.  The generic handler assumes that the entire file is
+data and there is a virtual hole at the end of the file.  So if the provided
+offset is less than i_size and SEEK_DATA is specified, return the same offset.
+If the above is true for the offset and you are given SEEK_HOLE, return the end
+of the file.  If the offset is i_size or greater return -ENXIO in either case.
diff --git a/trunk/fs/read_write.c b/trunk/fs/read_write.c
index 5520f8ad5504..5907b49e4d7e 100644
--- a/trunk/fs/read_write.c
+++ b/trunk/fs/read_write.c
@@ -64,6 +64,23 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
 			return file->f_pos;
 		offset += file->f_pos;
 		break;
+	case SEEK_DATA:
+		/*
+		 * In the generic case the entire file is data, so as long as
+		 * offset isn't at the end of the file then the offset is data.
+		 */
+		if (offset >= inode->i_size)
+			return -ENXIO;
+		break;
+	case SEEK_HOLE:
+		/*
+		 * There is a virtual hole at the end of the file, so as long as
+		 * offset isn't i_size or larger, return i_size.
+		 */
+		if (offset >= inode->i_size)
+			return -ENXIO;
+		offset = inode->i_size;
+		break;
 	}
 
 	if (offset < 0 && !unsigned_offsets(file))
@@ -128,12 +145,13 @@ EXPORT_SYMBOL(no_llseek);
 
 loff_t default_llseek(struct file *file, loff_t offset, int origin)
 {
+	struct inode *inode = file->f_path.dentry->d_inode;
 	loff_t retval;
 
-	mutex_lock(&file->f_dentry->d_inode->i_mutex);
+	mutex_lock(&inode->i_mutex);
 	switch (origin) {
 		case SEEK_END:
-			offset += i_size_read(file->f_path.dentry->d_inode);
+			offset += i_size_read(inode);
 			break;
 		case SEEK_CUR:
 			if (offset == 0) {
@@ -141,6 +159,26 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
 				goto out;
 			}
 			offset += file->f_pos;
+			break;
+		case SEEK_DATA:
+			/*
+			 * In the generic case the entire file is data, so as
+			 * long as offset isn't at the end of the file then the
+			 * offset is data.
+			 */
+			if (offset >= inode->i_size)
+				return -ENXIO;
+			break;
+		case SEEK_HOLE:
+			/*
+			 * There is a virtual hole at the end of the file, so
+			 * as long as offset isn't i_size or larger, return
+			 * i_size.
+			 */
+			if (offset >= inode->i_size)
+				return -ENXIO;
+			offset = inode->i_size;
+			break;
 	}
 	retval = -EINVAL;
 	if (offset >= 0 || unsigned_offsets(file)) {
@@ -151,7 +189,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
 		retval = offset;
 	}
 out:
-	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+	mutex_unlock(&inode->i_mutex);
 	return retval;
 }
 EXPORT_SYMBOL(default_llseek);
diff --git a/trunk/include/linux/fs.h b/trunk/include/linux/fs.h
index 824453be9fee..4a61f98823a6 100644
--- a/trunk/include/linux/fs.h
+++ b/trunk/include/linux/fs.h
@@ -32,7 +32,9 @@
 #define SEEK_SET	0	/* seek relative to beginning of file */
 #define SEEK_CUR	1	/* seek relative to current file position */
 #define SEEK_END	2	/* seek relative to end of file */
-#define SEEK_MAX	SEEK_END
+#define SEEK_DATA	3	/* seek to the next data */
+#define SEEK_HOLE	4	/* seek to the next hole */
+#define SEEK_MAX	SEEK_HOLE
 
 struct fstrim_range {
 	__u64 start;