[patch 04/10] udf: Use device size when drive reported bogus number of written blocks

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Jan Kara <jack@xxxxxxx>

commit 24a5d59f3477bcff4c069ff4d0ca9a3e037d0235 upstream.

Some drives report 0 as the number of written blocks when there are some blocks
recorded. Use device size in such case so that we can automagically mount such
media.

Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/udf/lowlevel.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/udf/lowlevel.c
+++ b/fs/udf/lowlevel.c
@@ -56,7 +56,12 @@ unsigned long udf_get_last_block(struct 
 	struct block_device *bdev = sb->s_bdev;
 	unsigned long lblock = 0;
 
-	if (ioctl_by_bdev(bdev, CDROM_LAST_WRITTEN, (unsigned long) &lblock))
+	/*
+	 * ioctl failed or returned obviously bogus value?
+	 * Try using the device size...
+	 */
+	if (ioctl_by_bdev(bdev, CDROM_LAST_WRITTEN, (unsigned long) &lblock) ||
+	    lblock == 0)
 		lblock = bdev->bd_inode->i_size >> sb->s_blocksize_bits;
 
 	if (lblock)


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