From 0aec09d049d7e994eba54bad4376dd8f58eab797 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 Aug 2014 07:32:06 -0400 Subject: [PATCH] drop ->s_umount around acct_auto_close() just repeat the frozen check after regaining it, and check that sb is still alive. If several threads hit acct_auto_close() at the same time, acct_auto_close() will survive that just fine. And we really don't want to play with writes and closing the file with ->s_umount held exclusive - it's a deadlock country. Signed-off-by: Al Viro --- fs/super.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/fs/super.c b/fs/super.c index 52ed93eb63df..a369f8964dc1 100644 --- a/fs/super.c +++ b/fs/super.c @@ -702,12 +702,22 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force) return -EACCES; #endif - if (flags & MS_RDONLY) - acct_auto_close(&sb->s_pins); - shrink_dcache_sb(sb); - remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); + if (remount_ro) { + if (sb->s_pins.first) { + up_write(&sb->s_umount); + acct_auto_close(&sb->s_pins); + down_write(&sb->s_umount); + if (!sb->s_root) + return 0; + if (sb->s_writers.frozen != SB_UNFROZEN) + return -EBUSY; + remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); + } + } + shrink_dcache_sb(sb); + /* If we are remounting RDONLY and current sb is read/write, make sure there are no rw files opened */ if (remount_ro) {