On Thu, Aug 19, 2010 at 10:15:25AM -0400, Jeff Layton wrote: > I'm looking at backporting some upstream changes to earlier kernels, > and ran across something I don't quite understand... > > In nfs_commit_unstable_pages, we set the flags to FLUSH_SYNC. We then > zero out the flags if wbc->nonblocking or wbc->for_background is set. > > Shouldn't we also clear it out if wbc->sync_mode == WB_SYNC_NONE ? > WB_SYNC_NONE means "don't wait on anything", so shouldn't that include > not waiting on the COMMIT to complete? I've been trying to figure out what the nonblocking flag is supposed to mean for a while now. It basically disappeared in commit 0d99519efef15fd0cf84a849492c7b1deee1e4b7 "writeback: remove unused nonblocking and congestion checks" from Wu. What's left these days is a couple of places in local copies of write_cache_pages (afs, cifs), and a couple of checks in random writepages instances (afs, block_write_full_page, ceph, nfs, reiserfs, xfs) and the use in nfs_write_inode. It's only actually set for memory migration and pageout, that is VM writeback. To me it really doesn't make much sense, but maybe someone has a better idea what it is for. > + if (wbc->nonblocking || wbc->for_background || > + wbc->sync_mode == WB_SYNC_NONE) You could remove the nonblocking and for_background checks as these impliy WB_SYNC_NONE. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>