Linux Storage and Filesystem Workshop, day 2 [LWN.net]

Linux Storage and Filesystem Workshop, day 2

Posted Apr 20, 2009 14:35 UTC (Mon) by willy (subscriber, #9762)
In reply to: Linux Storage and Filesystem Workshop, day 2 by giraffedata
Parent article: Linux Storage and Filesystem Workshop, day 2

The text from the standard says:

DESCRIPTION
The posix_fallocate() function shall ensure that any required storage for regular file data starting at offset and continuing for len bytes is allocated on the file system storage media. If posix_fallocate() returns successfully, subsequent writes to the specified file data shall not fail due to the lack of free space on the file system storage media.

I stand by my assertion that it is currently impossible to provide this with Thin Provisioning without actually writing to every single block.

(Log in to post comments)

Linux Storage and Filesystem Workshop, day 2

Posted Apr 20, 2009 16:05 UTC (Mon) by giraffedata (subscriber, #1954) [Link]

That's entirely consistent with what I wrote. There is space in the filesystem. (If there weren't, the write would fail with ENOSPC and statfs() would show no space).

The only problem is that writes to certain sectors of the storage medium fail for reasons out of the scope of POSIX.

There's layering going on here.