On Mon, Mar 29, 2010 at 8:01 AM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > tytso@xxxxxxx wrote: >> On Mon, Mar 29, 2010 at 09:48:50AM -0500, Eric Sandeen wrote: >>> CaT wrote: >>>> Using kernel 2.6.33.1. Am rsyncing from /data/mirror (a raid0 mount) to >>>> /dev/sda1 (a usb HD). Both filesystems formatted as ext3 but mounted as >>>> ext4. /mnt filesystem is only being added to and currently large files >>>> (iso files 700MB-4.4GB) are being copied. When I remounted /mnt as ext3 >>>> I could not duplicate the issue and the amount of disk used stabilised >>>> at 182G. The df results, whilst /mnt is mounted as ext4, are below: >>> I would say this is likely speculative allocation due to delalloc >>> (ext4 has to reserve worst-case metadata amounts to prepare for >>> delalloc writeback). When the file data actually gets written out, >>> the worst-case reservation is freed up again. We also flush and >>> switch to nodelalloc when the filesystem is pretty close to full. >>> see ext4_nonda_switch() for example. >>> >>> This looks pretty severe though, more than I would expect >>> from that behavior. >> >> This is fixed in commit d330a5bef, which which got merged post >> 2.6.34-rc2, and which we need to get into 2.6.33 stable. If you >> cherry-pick that commit, I think you'll see that it fixes this >> problem. > > Oh, right, spaced that one. Thanks for the reminder Ted. :) > > And from now on ext3-mounted-as-ext4 is special-cased so you won't get > delalloc, and you won't get this behavior at all (nor will you get > any delalloc benefits, FWIW). > Out of curiosity, when you say ext3-mounted-as-ext4, are you referring to filesystems without ext4 features mounted -t ext4, or filesystems mounted -t ext3 when CONFIG_EXT4_USE_FOR_EXT23 is defined? -Justin -- 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
