Re: linux-next: Tree for Jan 20 -- Kernel panic - Unable to mount root fs
On 01/21/2015 12:06 PM, Al Viro wrote:
On Wed, Jan 21, 2015 at 11:06:27AM -0800, Guenter Roeck wrote:
> On 01/21/2015 10:29 AM, Al Viro wrote:
>> On Wed, Jan 21, 2015 at 05:32:13AM -0800, Guenter Roeck wrote:
>>> Another data point (though I have no idea if it is useful or what it means):
>>>
>>> In the working case, path_init sets nd->flags to 0x50 or 0x51.
>>> In the non-working case (ie for all files with a '/' in the name),
>>> it sets nd->flags to 0x10 or 0x11, even though it is always called
>>> with the LOOKUP_RCU bit set in flags.
>>
>> Umm... Are those path_init() succeeding or failing? Note that path_init()
>> includes "walk everything except for the last component", so your
non-working
>> case is "have it walk anything at all". What's failing there?
path_init()
>> or handling the remaining component?
>>
> path_init() returns -2. Guess that explains the unexpected flags ;-).
> The failuere is from
> link_path_walk()
> walk_component()
Which is to say, lookup gave it a negative dentry. OK, let's just make
vfs_mkdir() and walk_component() print what they are doing; on top of
linux-next
diff --git a/fs/namei.c b/fs/namei.c
index 323957f..8a4e22f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1586,8 +1586,11 @@ static inline int walk_component(struct nameidata *nd, struct path
*path,
inode = path->dentry->d_inode;
}
err = -ENOENT;
- if (!inode || d_is_negative(path->dentry))
+ if (!inode || d_is_negative(path->dentry)) {
+ printk(KERN_ERR "walk_component[%p,%pd4] -> negative\n",
+ path->dentry, path->dentry);
goto out_path_put;
+ }
if (should_follow_link(path->dentry, follow)) {
if (nd->flags & LOOKUP_RCU) {
@@ -3521,6 +3524,7 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t
mode)
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error)
fsnotify_mkdir(dir, dentry);
+ printk(KERN_ERR "mkdir[%p,%pd4] => %d\n", dentry, dentry, error);
return error;
}
EXPORT_SYMBOL(vfs_mkdir);
ok case (putname commented out):
user_path_at_empty lookup usr flags 0x0
path_lookupat: calling path_init 'usr' flags=40
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=40[50] returned 0
walk_component: lookup_fast() returned 1
walk_component: lookup_slow() returned 0
walk_component: inode= (null), negative=1
do_path_lookup(usr, 0x10)
path_lookupat: calling path_init 'usr' flags=50
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=50[50] returned 0
mkdir[c74012a0,/usr] => 0
user_path_at_empty lookup usr flags 0x1
path_lookupat: calling path_init 'usr' flags=41
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=41[51] returned 0
walk_component: inode=c74004a0, negative=0
user_path_at_empty lookup usr flags 0x1
path_lookupat: calling path_init 'usr' flags=41
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=41[51] returned 0
failing case:
path_lookupat: calling path_init 'usr' flags=40
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=40[50] returned 0
walk_component: lookup_fast() returned 1
walk_component: lookup_slow() returned 0
walk_component: inode= (null), negative=1
do_path_lookup(usr, 0x10)
path_lookupat: calling path_init 'usr' flags=50
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=50[50] returned 0
mkdir[c74012a0,/kkk] => 0 <==== SIC!
user_path_at_empty lookup usr flags 0x1
path_lookupat: calling path_init 'usr' flags=41
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=41[51] returned 0
walk_component: lookup_fast() returned 1
walk_component: lookup_slow() returned 0
walk_component: inode= (null), negative=1
user_path_at_empty lookup usr flags 0x1
path_lookupat: calling path_init 'usr' flags=41
path_init: link_path_walk() returned 0
path_lookupat: path_init 'usr' flags=41[51] returned 0
walk_component: lookup_fast() returned 1
walk_component: lookup_slow() returned 0
walk_component: inode= (null), negative=1
Guenter