On Fri, May 13, 2011 at 06:40:13AM +0800, Dave Chinner wrote: > On Thu, May 12, 2011 at 09:57:07PM +0800, Wu Fengguang wrote: > > sync(2) is performed in two stages: the WB_SYNC_NONE sync and the > > WB_SYNC_ALL sync. Tag the first stage with wbc.tagged_sync and do > > livelock prevention for it, too. > > > > Note that writeback_inodes_sb() is called by not only sync(), they are > > treated the same because the other callers also need livelock prevention. > > > > Impact: It changes the order in which pages/inodes are synced to disk. > > Now in the WB_SYNC_NONE stage, it won't proceed to write the next inode > > until finished with the current inode. > > What about all the filesystems that implement their own > .writepages()/write_cache_pages() functions or have > have special code that checks WB_SYNC_ALL in .writepages (e.g. gfs2, > ext4, btrfs and perhaps others). Don't they all need to be aware of > this tagged_sync field? Right, good point. Currently only ext4 is updated. The other filesystems --- afs, btrfs, cifs, gfs2 --- do not even use PAGECACHE_TAG_TOWRITE for livelock prevention. My plan was to add PAGECACHE_TAG_TOWRITE and tagged_sync code to them as the next step, when tagged_sync is accepted and proved to work fine. Thanks, Fengguang -- 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
