From 38f21977663126fef53f5585e7f1653d8ebe55c4 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 6 Jan 2009 14:40:25 -0800 Subject: [PATCH] fs: sync_sb_inodes fix Fix data integrity semantics required by sys_sync, by iterating over all inodes and waiting for any writeback pages after the initial writeout. Comments explain the exact problem. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fs-writeback.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 53 insertions(+), 7 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index d99601a..a9ee474 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -440,6 +440,7 @@ void generic_sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc) { const unsigned long start = jiffies; /* livelock avoidance */ + int sync = wbc->sync_mode == WB_SYNC_ALL; spin_lock(&inode_lock); if (!wbc->for_kupdate || list_empty(&sb->s_io)) @@ -516,7 +517,49 @@ void generic_sync_sb_inodes(struct super_block *sb, if (!list_empty(&sb->s_more_io)) wbc->more_io = 1; } - spin_unlock(&inode_lock); + + if (sync) { + struct inode *inode, *old_inode = NULL; + + /* + * Data integrity sync. Must wait for all pages under writeback, + * because there may have been pages dirtied before our sync + * call, but which had writeout started before we write it out. + * In which case, the inode may not be on the dirty list, but + * we still have to wait for that writeout. + */ + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { + struct address_space *mapping; + + if (inode->i_state & (I_FREEING|I_WILL_FREE)) + continue; + mapping = inode->i_mapping; + if (mapping->nrpages == 0) + continue; + __iget(inode); + spin_unlock(&inode_lock); + /* + * We hold a reference to 'inode' so it couldn't have + * been removed from s_inodes list while we dropped the + * inode_lock. We cannot iput the inode now as we can + * be holding the last reference and we cannot iput it + * under inode_lock. So we keep the reference and iput + * it later. + */ + iput(old_inode); + old_inode = inode; + + filemap_fdatawait(mapping); + + cond_resched(); + + spin_lock(&inode_lock); + } + spin_unlock(&inode_lock); + iput(old_inode); + } else + spin_unlock(&inode_lock); + return; /* Leave any unwritten inodes on s_io */ } EXPORT_SYMBOL_GPL(generic_sync_sb_inodes); @@ -596,13 +639,16 @@ void sync_inodes_sb(struct super_block *sb, int wait) .range_start = 0, .range_end = LLONG_MAX, }; - unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY); - unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS); - wbc.nr_to_write = nr_dirty + nr_unstable + - (inodes_stat.nr_inodes - inodes_stat.nr_unused) + - nr_dirty + nr_unstable; - wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */ + if (!wait) { + unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY); + unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS); + + wbc.nr_to_write = nr_dirty + nr_unstable + + (inodes_stat.nr_inodes - inodes_stat.nr_unused); + } else + wbc.nr_to_write = LONG_MAX; /* doesn't actually matter */ + sync_sb_inodes(sb, &wbc); } -- 1.8.2.3