On Wed, May 27, 2020 at 02:16:00PM +0300, Amir Goldstein wrote:
> On Wed, May 27, 2020 at 6:45 AM yangerkun <yangerkun@xxxxxxxxxx> wrote:
> >
> > Run generic/461 with ext4 upper/lower layer sometimes may trigger the
> > bug as below(linux 4.19):
> >
> > [ 551.001349] overlayfs: failed to get metacopy (-5)
> > [ 551.003464] overlayfs: failed to get inode (-5)
> > [ 551.004243] overlayfs: cleanup of 'd44/fd51' failed (-5)
> > [ 551.004941] overlayfs: failed to get origin (-5)
> > [ 551.005199] ------------[ cut here ]------------
> > [ 551.006697] WARNING: CPU: 3 PID: 24674 at fs/inode.c:1528 iput+0x33b/0x400
> > ...
> > [ 551.027219] Call Trace:
> > [ 551.027623] ovl_create_object+0x13f/0x170
> > [ 551.028268] ovl_create+0x27/0x30
> > [ 551.028799] path_openat+0x1a35/0x1ea0
> > [ 551.029377] do_filp_open+0xad/0x160
> > [ 551.029944] ? vfs_writev+0xe9/0x170
> > [ 551.030499] ? page_counter_try_charge+0x77/0x120
> > [ 551.031245] ? __alloc_fd+0x160/0x2a0
> > [ 551.031832] ? do_sys_open+0x189/0x340
> > [ 551.032417] ? get_unused_fd_flags+0x34/0x40
> > [ 551.033081] do_sys_open+0x189/0x340
> > [ 551.033632] __x64_sys_creat+0x24/0x30
> > [ 551.034219] do_syscall_64+0xd5/0x430
> > [ 551.034800] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > ...
> > [ 556.107515] BUG: Dentry 000000006bc1d73f{i=4129c,n=fd51} still in use (-1) [unmount of ext4 sdb]
> > [ 556.108946] ------------[ cut here ]------------
> > [ 556.109686] WARNING: CPU: 1 PID: 24682 at fs/dcache.c:1557 umount_check+0x95/0xc0
> > [ 556.130343] d_walk+0x10d/0x430
> > [ 556.130832] do_one_tree+0x30/0x60
> > [ 556.131365] shrink_dcache_for_umount+0x38/0xe0
> > [ 556.132063] generic_shutdown_super+0x2e/0x1c0
> > [ 556.132747] kill_block_super+0x29/0x80
> > [ 556.133338] deactivate_locked_super+0x7a/0x100
> > [ 556.134034] deactivate_super+0x9d/0xb0
> > [ 556.134627] cleanup_mnt+0x67/0x100
> > [ 556.135173] __cleanup_mnt+0x16/0x20
> > [ 556.135731] task_work_run+0xdb/0x110
> > [ 556.136306] exit_to_usermode_loop+0x197/0x1b0
> > [ 556.136991] do_syscall_64+0x3ce/0x430
> > [ 556.137571] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > ...
> > [ 556.378140] VFS: Busy inodes after unmount of sdb. Self-destruct in 5 seconds. Have a nice day...
> >
> > After check the code, there may some bug need to fix:
> > 1. We need to call iput once ovl_check_metacopy_xattr fail.
> > 2. We need to call unlock_new_inode or the above iput(also with iput in
> > ovl_create_object) will trigger the a WARN_ON since the I_NEW still
> > exists.
> > 3. We should move the init for upperdentry to the place below
> > ovl_check_metacopy_xattr. Or the dentry reference will decrease to
> > -1(error path in ovl_create_upper will inc, ovl_destroy_inode too).
> >
>
> OR we don't check metacopy xattr in ovl_get_inode().
>
> In ovl_lookup() we already checked metacopy xattr.
> No reason to check it again in this subtle context.
>
> In ovl_lookup() can store value of upper metacopy and after we get
> the inode, set the OVL_UPPERDATA inode flag according to
> upperdentry && !uppermetacopy.
>
> That would be consistent with ovl_obtain_alias() which sets the
> OVL_UPPERDATA inode flag after getting the inode.
Hi Amir,
This patch implements what you are suggesting. Compile tested only.
Does this look ok?
May be I don't need to split it up in lmetacopy and umetacopy. Ideally,
lookup in lower layers should stop if an upper regular file is not
metacopy. IOW, (upperdentry && !metacopy) might be sufficient check.
Will look closely if this patch looks fine.
Thanks
Vivek
---
fs/overlayfs/inode.c | 11 +----------
fs/overlayfs/namei.c | 12 +++++++-----
2 files changed, 8 insertions(+), 15 deletions(-)
Index: redhat-linux/fs/overlayfs/namei.c
===================================================================
--- redhat-linux.orig/fs/overlayfs/namei.c 2020-04-13 13:52:53.438294244 -0400
+++ redhat-linux/fs/overlayfs/namei.c 2020-05-27 15:28:38.242809626 -0400
@@ -823,7 +823,7 @@ struct dentry *ovl_lookup(struct inode *
struct dentry *this;
unsigned int i;
int err;
- bool metacopy = false;
+ bool lmetacopy = false, umetacopy=false;
struct ovl_lookup_data d = {
.sb = dentry->d_sb,
.name = dentry->d_name,
@@ -869,7 +869,7 @@ struct dentry *ovl_lookup(struct inode *
goto out_put_upper;
if (d.metacopy)
- metacopy = true;
+ umetacopy = true;
}
if (d.redirect) {
@@ -941,7 +941,7 @@ struct dentry *ovl_lookup(struct inode *
}
if (d.metacopy)
- metacopy = true;
+ lmetacopy = true;
/*
* Do not store intermediate metacopy dentries in chain,
* except top most lower metacopy dentry
@@ -982,7 +982,7 @@ struct dentry *ovl_lookup(struct inode *
}
}
- if (metacopy) {
+ if (lmetacopy || umetacopy) {
/*
* Found a metacopy dentry but did not find corresponding
* data dentry
@@ -1023,7 +1023,7 @@ struct dentry *ovl_lookup(struct inode *
*
* Always lookup index of non-dir non-metacopy and non-upper.
*/
- if (ctr && (!upperdentry || (!d.is_dir && !metacopy)))
+ if (ctr && (!upperdentry || (!d.is_dir && !(lmetacopy || umetacopy))))
origin = stack[0].dentry;
if (origin && ovl_indexdir(dentry->d_sb) &&
@@ -1074,6 +1074,8 @@ struct dentry *ovl_lookup(struct inode *
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out_free_oe;
+ if (upperdentry && !umetacopy)
+ ovl_set_flag(OVL_UPPERDATA, inode);
}
ovl_dentry_update_reval(dentry, upperdentry,
Index: redhat-linux/fs/overlayfs/inode.c
===================================================================
--- redhat-linux.orig/fs/overlayfs/inode.c 2020-04-22 11:32:28.237700957 -0400
+++ redhat-linux/fs/overlayfs/inode.c 2020-05-27 15:30:21.059809626 -0400
@@ -939,7 +939,7 @@ struct inode *ovl_get_inode(struct super
bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry,
oip->index);
int fsid = bylower ? lowerpath->layer->fsid : 0;
- bool is_dir, metacopy = false;
+ bool is_dir;
unsigned long ino = 0;
int err = oip->newinode ? -EEXIST : -ENOMEM;
@@ -1000,15 +1000,6 @@ struct inode *ovl_get_inode(struct super
if (oip->index)
ovl_set_flag(OVL_INDEX, inode);
- if (upperdentry) {
- err = ovl_check_metacopy_xattr(upperdentry);
- if (err < 0)
- goto out_err;
- metacopy = err;
- if (!metacopy)
- ovl_set_flag(OVL_UPPERDATA, inode);
- }
-
OVL_I(inode)->redirect = oip->redirect;
if (bylower)
