Daniel Phillips <daniel@xxxxxxxxx> writes: > Hi Dave, > On 06/02/2014 08:33 PM, Dave Chinner wrote: >> On Mon, Jun 02, 2014 at 01:02:29PM -0700, Daniel Phillips wrote: >>> >>> Redirty_tail nearly works, but "if (!list_empty(&wb->b_dirty))" is >>> not correct because the inode needs to end up on the dirty list >>> whether it was already there or not. >> redirty_tail() always moves the inode to the end of the dirty >> list. It doesn't move inode to end of the dirty if wb.b_dirty is empty (I.e. it can move from wb.b_io to wb.b_dirty too). BTW, this is called for like mark inode dirty process, not always writeback path. >>> This requirement is analogous to __mark_inode_dirty() and must >>> tolerate similar races. At the microoptimization level, calling >>> redirty_tail from inode_writeback_touch would be less efficient >>> and more bulky. Another small issue is, redirty_tail does not >>> always update the timestamp, which could trigger some bogus >>> writeback events. >> redirty_tail does not update the timestamp when it doesn't need to >> change. If it needs to be changed because the current value would >> violate the time ordering requirements of the list, it rewrites it. >> >> So there is essentially no functional difference between the new >> function and redirty_tail.... > > Hirofumi, would you care to comment? It has difference. Say, tail->dirtied_when == 1, inode->dirtied_when == 2, and now == 30 (tail->dirtied_when is expired at 31 with default config). In this case, redirty_tail() doesn't update ->dirtied_when. And if inode->dirtied_when is not updated to 30, expire time has difference. I.e. 32 vs 60. Thanks. -- OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
