On 02.07.25 14:17, Christian Brauner wrote: > On Wed, Jul 02, 2025 at 11:47:58AM +0100, André Draszik wrote: >> Hi, >> >> On Sun, 2025-06-22 at 23:38 -0700, Song Liu wrote: >>> From: Christian Brauner <brauner@xxxxxxxxxx> >>> >>> All allocations of struct kernfs_iattrs are serialized through a global >>> mutex. Simply do a racy allocation and let the first one win. I bet most >>> callers are under inode->i_rwsem anyway and it wouldn't be needed but >>> let's not require that. >>> >>> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> >>> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> >>> Acked-by: Tejun Heo <tj@xxxxxxxxxx> >>> Signed-off-by: Song Liu <song@xxxxxxxxxx> >> >> On next-20250701, ls -lA gives errors on /sys: >> >> $ ls -lA /sys/ >> ls: /sys/: No data available >> ls: /sys/kernel: No data available >> ls: /sys/power: No data available >> ls: /sys/class: No data available >> ls: /sys/devices: No data available >> ls: /sys/dev: No data available >> ls: /sys/hypervisor: No data available >> ls: /sys/fs: No data available >> ls: /sys/bus: No data available >> ls: /sys/firmware: No data available >> ls: /sys/block: No data available >> ls: /sys/module: No data available >> total 0 >> drwxr-xr-x 2 root root 0 Jan 1 1970 block >> drwxr-xr-x 52 root root 0 Jan 1 1970 bus >> drwxr-xr-x 88 root root 0 Jan 1 1970 class >> drwxr-xr-x 4 root root 0 Jan 1 1970 dev >> drwxr-xr-x 11 root root 0 Jan 1 1970 devices >> drwxr-xr-x 3 root root 0 Jan 1 1970 firmware >> drwxr-xr-x 10 root root 0 Jan 1 1970 fs >> drwxr-xr-x 2 root root 0 Jul 2 09:43 hypervisor >> drwxr-xr-x 14 root root 0 Jan 1 1970 kernel >> drwxr-xr-x 251 root root 0 Jan 1 1970 module >> drwxr-xr-x 3 root root 0 Jul 2 09:43 power >> >> >> and my bisect is pointing to this commit. Simply reverting it also fixes >> the errors. >> >> >> Do you have any suggestions? > > Yes, apparently the xattr selftest don't cover sysfs/kernfs. The issue > is that the commit changed listxattr() to skip allocation of the xattr > header and instead just returned ENODATA. We should just allocate like > before tested just now: > > user1@localhost:~$ sudo ls -al /sys/kernel/ > total 0 > drwxr-xr-x 17 root root 0 Jul 2 13:41 . > dr-xr-xr-x 12 root root 0 Jul 2 13:41 .. > -r--r--r-- 1 root root 4096 Jul 2 13:41 address_bits > drwxr-xr-x 3 root root 0 Jul 2 13:41 boot_params > drwxr-xr-x 2 root root 0 Jul 2 13:41 btf > drwxr-xr-x 2 root root 0 Jul 2 13:41 cgroup > drwxr-xr-x 2 root root 0 Jul 2 13:41 config > -r--r--r-- 1 root root 4096 Jul 2 13:41 cpu_byteorder > -r--r--r-- 1 root root 4096 Jul 2 13:41 crash_elfcorehdr_size > drwx------ 34 root root 0 Jul 2 13:41 debug > -r--r--r-- 1 root root 4096 Jul 2 13:41 fscaps > -r--r--r-- 1 root root 4096 Jul 2 13:41 hardlockup_count > drwxr-xr-x 2 root root 0 Jul 2 13:41 iommu_groups > drwxr-xr-x 344 root root 0 Jul 2 13:41 irq > -r--r--r-- 1 root root 4096 Jul 2 13:41 kexec_crash_loaded > -rw-r--r-- 1 root root 4096 Jul 2 13:41 kexec_crash_size > -r--r--r-- 1 root root 4096 Jul 2 13:41 kexec_loaded > drwxr-xr-x 9 root root 0 Jul 2 13:41 mm > -r--r--r-- 1 root root 84 Jul 2 13:41 notes > -r--r--r-- 1 root root 4096 Jul 2 13:41 oops_count > -rw-r--r-- 1 root root 4096 Jul 2 13:41 profiling > -rw-r--r-- 1 root root 4096 Jul 2 13:41 rcu_expedited > -rw-r--r-- 1 root root 4096 Jul 2 13:41 rcu_normal > -r--r--r-- 1 root root 4096 Jul 2 13:41 rcu_stall_count > drwxr-xr-x 2 root root 0 Jul 2 13:41 reboot > drwxr-xr-x 2 root root 0 Jul 2 13:41 sched_ext > drwxr-xr-x 4 root root 0 Jul 2 13:41 security > drwxr-xr-x 190 root root 0 Jul 2 13:41 slab > -r--r--r-- 1 root root 4096 Jul 2 13:41 softlockup_count > drwxr-xr-x 2 root root 0 Jul 2 13:41 software_nodes > drwxr-xr-x 4 root root 0 Jul 2 13:41 sunrpc > drwxr-xr-x 6 root root 0 Jul 2 13:41 tracing > -r--r--r-- 1 root root 4096 Jul 2 13:41 uevent_seqnum > -r--r--r-- 1 root root 4096 Jul 2 13:41 vmcoreinfo > -r--r--r-- 1 root root 4096 Jul 2 13:41 warn_count > > I'm folding: > > diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c > index 3c293a5a21b1..457f91c412d4 100644 > --- a/fs/kernfs/inode.c > +++ b/fs/kernfs/inode.c > @@ -142,9 +142,9 @@ ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size) > struct kernfs_node *kn = kernfs_dentry_node(dentry); > struct kernfs_iattrs *attrs; > > - attrs = kernfs_iattrs_noalloc(kn); > + attrs = kernfs_iattrs(kn); > if (!attrs) > - return -ENODATA; > + return -ENOMEM; > > return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); > } > > which brings it back to the old behavior. > ...but it looks like v3 was merged as-is in the end, without this fixup. Is there some separate patch in the pipeline, or was this forgotten? > I'm also adding a selftest for this behavior. Patch appended. Jan -- Siemens AG, Foundational Technologies Linux Expert Center
