diff options
| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2020-04-09 11:29:47 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-05-13 11:11:24 +0200 |
| commit | 32b1924b210a70dcacdf65abd687c5ef86a67541 (patch) | |
| tree | 19372bfcaac553c2f8dd787e13fd0a8f23039cb2 /fs | |
| parent | 62a8a85be8355b01330667c2b4676fb60c184380 (diff) | |
ovl: skip overlayfs superblocks at global sync
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 <dmtrmonakhov@yandex-team.ru>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/overlayfs/super.c | 5 | ||||
| -rw-r--r-- | fs/sync.c | 3 |
2 files changed, 5 insertions, 3 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 6e3fa96613f5..f57aa348dcd6 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -261,8 +261,8 @@ static int ovl_sync_fs(struct super_block *sb, int wait) return 0; /* - * If this is a sync(2) call or an emergency sync, all the super blocks - * will be iterated, including upper_sb, so no need to do anything. + * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC). + * All the super blocks will be iterated, including upper_sb. * * If this is a syncfs(2) call, then we do need to call * sync_filesystem() on upper_sb, but enough if we do it when being @@ -1870,6 +1870,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) sb->s_xattr = ovl_xattr_handlers; sb->s_fs_info = ofs; sb->s_flags |= SB_POSIXACL; + sb->s_iflags |= SB_I_SKIP_SYNC; err = -ENOMEM; root_dentry = ovl_get_root(sb, upperpath.dentry, oe); diff --git a/fs/sync.c b/fs/sync.c index 4d1ff010bc5a..16c2630ee4bf 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -76,7 +76,8 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg) static void sync_fs_one_sb(struct super_block *sb, void *arg) { - if (!sb_rdonly(sb) && sb->s_op->sync_fs) + if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) && + sb->s_op->sync_fs) sb->s_op->sync_fs(sb, *(int *)arg); } |