On Oct 29, 2011, at 6:52 PM, "Peter Teoh" <[email protected]> wrote:
> On Sat, Oct 29, 2011 at 6:03 AM, Mike Gibson > <[email protected]> wrote: >> I'm updating a user space program that finds free blocks on a ext2/3 >> filesystem so that it works with ext4. I'm concerned about how extents >> might affect my program. My program currently looks only at the block >> allocation bitmaps. Are the block allocation bitmaps still updated when an >> extent is created? >> > > problem is what u see as free blocks may not be seen at the kernel > level as free block.....since u not holding any locks, there may be > situation when your block allocation may conflict with that of the > kernel, then u will get disastrous irrecoverable errors - worst case > is your userspace data get overwritten by kernel. > > i supposed it is a legacy program, but there exists a small > probability that this problem will occur. This is only used when the filesystem is offline, so I'm only interested in the on disk structure. Mike Gibson _______________________________________________ Kernelnewbies mailing list [email protected] http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
