Hi, I am trying to understand the expectation on filesystem writepages by __fsync_super -> generic_sync_sb_inodes call path. __fsync_super make two calls to generic_sync_sb_inodes and the second call is made with WB_SYNC_ALL. The problem is, i am finding multiple ways we may 'break' from the generic_sync_sb_inodes while (!list_empty(&sb->s_io)) loop. For ex: a) When wbc->nr_to_write <=0 This should normally indicate that we wrote more than we requested That means we have more dirty pages . So why break from loop ? This may be ok for nr_to_write limited writeback. But is it ok for __fsync_super ? b) pages_skipped != wbc->pages_skipped. That means writepages was not able to write some of the pages and it redirtied the same. We add such inode to s_dirty list. But we don't loop through the s_dirty list later trying to write the dirty pages. We actually call generic_sync_sb_inodes again. That can actually cause s_dirty list content to move to s_io once via queue_io. But then we can have pages skipped again in the second call to generic_sync_sb_inodes ? Shouldn't we have a variant that actually loop trough s_dirty and s_more_io list MULTIPLE times and make sure we force all the dirty pages to disk before __fsync_super returns ? Or is there an expectation from file system writepages that would make sure calling generic_sync_sb_inodes TWICE would guarantee that ? -aneesh -- 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
