Hi Filipe On 2013-11-19 17:06, Filipe David Manana wrote: > On Wed, Nov 13, 2013 at 6:59 PM, Goffredo Baroncelli <kreijack@xxxxxxxxx> wrote: >> Hi Filipe, >> >> my comments below >> On 2013-11-13 02:21, Filipe David Borba Manana wrote: >>> This change adds infrastructure to allow for generic properties for >>> inodes. Properties are name/value pairs that can be associated with >>> inodes for different purposes. They're stored as xattrs with the >>> prefix "btrfs." [...] > >> >> Moreover I have a doubt about the opportunity to store the information >> like the compression both in inode and in the xattr: what happens if the >> user does an "chattr -c" ? The xattr will be not updated. > > Right, there was no interaction the compression attr/flag. > The next patch version adds such interaction. > >> I suggest to update/create a real xattr only if there is no space for >> the new information in the inode. In the other case the xattr should be >> a fake xattr to get/set the property stored in the inode (or whichever >> is involved). >> >> Of course also the function btrfs_listxattr() should be updated to show >> the "fake" xattr which doesn't have a real xattr stored on the disk. The >> same is true for the getxattr() function... > > Adding such fake on the fly stuff seems too complex imho. Just > adding/removing the xattr compression properties on chattr +c/-c seems > simpler and more intuitive. Looking at btrfs_listxattr() it seems that the xattr listing is done in a very simple way: the function *listxattr() returns a buffer filled with all the xattr as a zero terminated strings sequences. Because the "fake" attribute are know in advance, listing these became a memcpy() of a bytes of buffer statically allocated. GB -- gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
