linux-ext4 - [PATCH RESEND] vfs: Return EINVAL for default SEEK_HOLE, SEEK

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Date:	Fri, 10 Oct 2014 16:23:40 +0200
From:	Jan Kara <jack@...e.cz>
To:	linux-fsdevel@...r.kernel.org
Cc:	linux-ext4@...r.kernel.org, Dave Chinner <david@...morbit.com>,
	xfs@....sgi.com, cluster-devel@...hat.com,
	Steven Whitehouse <swhiteho@...hat.com>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>, ocfs2-devel@....oracle.com,
	reiserfs-devel@...r.kernel.org, Jeff Mahoney <jeffm@...e.de>,
	Dave Kleikamp <shaggy@...nel.org>,
	jfs-discussion@...ts.sourceforge.net, tytso@....edu,
	viro@...iv.linux.org.uk, Jan Kara <jack@...e.cz>
Subject: [PATCH RESEND] vfs: Return EINVAL for default SEEK_HOLE, SEEK_DATA implementation

Generic implementation of SEEK_HOLE & SEEK_DATA in
generic_file_llseek_size() and default_llseek() behaved as if everything
within i_size is data and everything beyond i_size is a hole. That makes
sense at the first sight (and definitely is a valid implementation of
the spec) but at the second sight it isn't very useful. If anyone
bothers with looking for holes / data, he should be better told we don't
really know so that he can fall back to his chosen backup strategy
(think of e.g. cp(1)).

This is a userspace API change however the kernel interface is there
only for two years so hopefully userspace is still prepared to handle
EINVAL return value.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/read_write.c | 38 ++------------------------------------
 1 file changed, 2 insertions(+), 36 deletions(-)

Al, what do you think about this change?

diff --git a/fs/read_write.c b/fs/read_write.c
index edc5746a902a..71525d75742f 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -111,22 +111,8 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		spin_unlock(&file->f_lock);
 		return offset;
 	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 >= eof)
-			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 >= eof)
-			return -ENXIO;
-		offset = eof;
-		break;
+		return -EINVAL;
 	}
 
 	return vfs_setpos(file, offset, maxsize);
@@ -214,28 +200,8 @@ loff_t default_llseek(struct file *file, loff_t offset, int whence)
 			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) {
-				retval = -ENXIO;
-				goto out;
-			}
-			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) {
-				retval = -ENXIO;
-				goto out;
-			}
-			offset = inode->i_size;
-			break;
+			return -EINVAL;
 	}
 	retval = -EINVAL;
 	if (offset >= 0 || unsigned_offsets(file)) {
-- 
1.8.1.4

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