On jeu, 2007-03-29 at 13:59 -0600, Andreas Dilger wrote:
On Mar 29, 2007 14:17 +0200, Vincent Caron wrote:
I just noticed that 'tune2fs -l' did not returned a lively updated
information regarding the free inodes count (looks like it's always
correct after unmounting).
This is a bit of a defect in all 2.6 kernels. They never update the
on disk superblock free blocks/inodes information to avoid lock contention,
even if this info is available.
It turns out it is okay in my case since 'df -i' reports correct
numbers.
Can you please give the following patch a try? It fixes this issue,
and also makes statfs MUCH more efficient for large filesystems, because
the filesystem overhead is constant unless the filesystem size changes
and checking that for 16k groups is slow (hence hack to add cond_resched()
instead of fixing problem correctly). It has not been tested much, but
is very straight forward.
Only the last part is strictly necessary to fix your particular problem
(setting of es-s_free_inodes_count and es-s_free_blocks_count). This
is lazy, in the sense that you need a statfs to update the count, and
then a truncate or unlink or rmdir in order to dirty the superblock to
flush it to disk. However, it will be correct in the buffer cache, and
it is a lot better than what we have now. We don't want a non-lazy version
anyways, because of performance.
Unfortunately the problem shows on a production machine and I don't
have a similar one to test properly (it's a heavy-loaded filer).
BTW, if ondisk superblocks are not updated until specific events occur
(umount, statfs), what is the consequence of a system crash ? Does
journalization come into play (superblock=metadata?), does fsck fixes
figures from other ondisk structures ? Just being curious...
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