From 410fb31d899a19d3514aa9a8fa8b17bac5f5549a Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Thu, 9 Apr 2020 11:29:47 +0300 Subject: ovl: skip overlayfs superblocks at global sync [ Upstream commit 32b1924b210a70dcacdf65abd687c5ef86a67541 ] Stacked filesystems like overlayfs has no own writeback, but they have to forward syncfs() requests to backend for keeping data integrity. During global sync() each overlayfs instance calls method ->sync_fs() for backend although it itself is in global list of superblocks too. As a result one syscall sync() could write one superblock several times and send multiple disk barriers. This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that. Reported-by: Dmitry Monakhov Signed-off-by: Konstantin Khlebnikov Reviewed-by: Amir Goldstein Signed-off-by: Miklos Szeredi Stable-dep-of: b836c4d29f27 ("ima: detect changes to the backing overlay file") Signed-off-by: Sasha Levin --- include/linux/fs.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 95b8ef09b76c..f89748aac8c3 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1351,6 +1351,8 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 #define SB_I_UNTRUSTED_MOUNTER 0x00000040 +#define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */ + /* Possible states of 'frozen' field */ enum { SB_UNFROZEN = 0, /* FS is unfrozen */ -- cgit v1.2.3