On Tue, Sep 29, 2009 at 11:47:19AM -0500, Eric Sandeen wrote: > I was running some of the xfstests enospc tests on ext4, and they were > failing; in one case, manymanymany small files are made to fill up a > 100M filesystem. ext4 stops quite early with -ENOSPC, but after a bit, > (or after a "sync") we get 40MB free again. So 40% of the fs space is > hidden somewhere in preallocation... > > I tried calling out to discard group prealloc but that's only a few > blocks. I'll go trace through the sync paths to see what all gets > released, but if anyone knows offhand where the rest of that space is > hiding, please give me a shout. :) > preallocation space is discarded by default if we fail a block allocation ext4_mb_discard_preallocations does that. What might be happening is the extra meta data blocks that we reserve for making sure we will be able to properly insert the new extent on block allocation. I guess we should force a data allocation when we fail with ENOSPC in ext4_da_writepages We currently force a journal commit so that the we claim back the blocks from deleted files. But we can also force block allocation for delayed allocated inodes so that we free some of the extra meta data we reserved -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
