mounted loopback device suddendly become read only

[thierrybo]

Hi,

I have a "strange" problem. I use an usb disk connected to my nas to make backups. I use backintime (rsync) and to use hard links to save disk space, I created a "sparse" file on this usb disk. Then I mount it as ext4 on loopback device.

I can browse this sparse file (as root) and create files.

However each time I run the backup job, after a couple of minutes, rsync outputs errors messages because the filesystem is read only. For some unexplained reason, the filesystem switch from rw to ro after writing some files on it. I can't see any reason for that. The drive is empty, 500 Mb, and the only file is the spare file (490 Mb) withe 6Mb used.