Thank you for the fix
This fixes blk devices hang issues on AMD EPYC x86 systems.
Tested-by: Ayush Jain <Ayush.jain3@xxxxxxx>
On 4/23/2025 10:29 AM, Christoph Hellwig wrote:
> The recent move of the bdev_statx call to the low-level vfs_getattr_nosec
> helper caused it being used by devtmpfs, which leads to deadlocks in
> md teardown due to the block device lookup and put interfering with the
> unusual lifetime rules in md.
>
> But as handle_remove only works on inodes created and owned by devtmpfs
> itself there is no need to use vfs_getattr_nosec vs simply reading the
> mode from the inode directly. Switch to that to avoid the bdev lookup
> or any other unintentional side effect.
>
> Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> Reported-by: Xiao Ni <xni@xxxxxxxxxx>
> Fixes: 777d0961ff95 ("fs: move the bdex_statx call to vfs_getattr_nosec")
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> Tested-by: Xiao Ni <xni@xxxxxxxxxx>
> ---
> drivers/base/devtmpfs.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
> index 6dd1a8860f1c..53fb0829eb7b 100644
> --- a/drivers/base/devtmpfs.c
> +++ b/drivers/base/devtmpfs.c
> @@ -296,7 +296,7 @@ static int delete_path(const char *nodepath)
> return err;
> }
>
> -static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
> +static int dev_mynode(struct device *dev, struct inode *inode)
> {
> /* did we create it */
> if (inode->i_private != &thread)
> @@ -304,13 +304,13 @@ static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *sta
>
> /* does the dev_t match */
> if (is_blockdev(dev)) {
> - if (!S_ISBLK(stat->mode))
> + if (!S_ISBLK(inode->i_mode))
> return 0;
> } else {
> - if (!S_ISCHR(stat->mode))
> + if (!S_ISCHR(inode->i_mode))
> return 0;
> }
> - if (stat->rdev != dev->devt)
> + if (inode->i_rdev != dev->devt)
> return 0;
>
> /* ours */
> @@ -321,8 +321,7 @@ static int handle_remove(const char *nodename, struct device *dev)
> {
> struct path parent;
> struct dentry *dentry;
> - struct kstat stat;
> - struct path p;
> + struct inode *inode;
> int deleted = 0;
> int err;
>
> @@ -330,11 +329,8 @@ static int handle_remove(const char *nodename, struct device *dev)
> if (IS_ERR(dentry))
> return PTR_ERR(dentry);
>
> - p.mnt = parent.mnt;
> - p.dentry = dentry;
> - err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
> - AT_STATX_SYNC_AS_STAT);
> - if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
> + inode = d_inode(dentry);
> + if (dev_mynode(dev, inode)) {
> struct iattr newattrs;
> /*
> * before unlinking this node, reset permissions
> @@ -342,7 +338,7 @@ static int handle_remove(const char *nodename, struct device *dev)
> */
> newattrs.ia_uid = GLOBAL_ROOT_UID;
> newattrs.ia_gid = GLOBAL_ROOT_GID;
> - newattrs.ia_mode = stat.mode & ~0777;
> + newattrs.ia_mode = inode->i_mode & ~0777;
> newattrs.ia_valid =
> ATTR_UID|ATTR_GID|ATTR_MODE;
> inode_lock(d_inode(dentry));
