| title: | Re PATCH 00 32 VFS based Union Mount V3 |
|
On Tue, 19 May 2009, Jan Blunck wrote:
The directory in the topmost filesystem is created during
lookup. The contents of the directory isnt copied up presistently
at that point in time. Therefore you have an empty directory in the
topmost filesystem after the lookup. This was necessary to get rid
of the union_relookup_topmost() calls during create, mknod, mkdir
etc.
When readdir is called, the topmost directory is filed up with
fallthru entries which are persistently stored. This is only
necessary to get readdir right wrt POSIX. During lookup the fallthru
dentry, which is in fact a special negative dentry, is ignored and
therefore the lookup continues on the lower filesystem.
So this means that the topmost branch always needs to be writable,
right? It isnt possible to make a union of two iso9660 filesystems,
for example?
Thanks,
Miklos
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at rel="nofollow" vger.kernel.org/majordomo-info.html vger.kernel.org/majordomo-info.html
|
