[PATCH v7 07/12] kernfs: hold kernfs_iattr_rwsem when initializing a new inode
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COOLING8d
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From: Jori Koolstra <jkoolstra@xs4all.nl>
Date: 2026-10-16 14:37:20
Also in:
linux-fsdevel, lkml
Subsystem:
filesystems (vfs and infrastructure), kernfs, the rest · Maintainers:
Alexander Viro, Christian Brauner, Greg Kroah-Hartman, Tejun Heo, Linus Torvalds
Revision v7 of 9 in this series.
Revisions (9)
kernfs_refresh_inode() copies the uid, gid, timestamps and nlink of a
kernfs_node into its VFS inode. Since commit 9caf69614225 ("kernfs:
Introduce separate rwsem to protect inode attributes.") these are
protected by kernfs_iattr_rwsem.
kernfs_init_inode() calls kernfs_refresh_inode(), but was not converted.
Its callers in turn hold kernfs_rwsem (kernfs_iop_lookup(),
kernfs_fill_super()) or no lock at all (__kernfs_fh_to_dentry()),
neither of which excludes a concurrent
kernfs_setattr()/kernfs_iop_setattr().
Take kernfs_iattr_rwsem for reading around the refresh in
kernfs_init_inode(). This nests inside kernfs_rwsem, which matches
kernfs_link_sibling() and kernfs_unlink_sibling().
Also, kernfs_get_inode() then does not need to hold kernfs_rwsem, so
drop it from kernfs_fill_super().
Fixes: 9caf69614225 ("kernfs: Introduce separate rwsem to protect inode attributes.")
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
---
fs/kernfs/inode.c | 3 ++-
fs/kernfs/mount.c | 3 ---
2 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index abb286bc3474..83f2007498db 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c@@ -204,7 +204,8 @@ static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) inode->i_generation = kernfs_gen(kn); set_default_inode_attr(inode, kn->mode); - kernfs_refresh_inode(kn, inode); + scoped_guard(rwsem_read, &kernfs_root(kn)->kernfs_iattr_rwsem) + kernfs_refresh_inode(kn, inode); /* initialize inode according to type */ switch (kernfs_type(kn)) {
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index a57399021c8b..202a5ca2bd34 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c@@ -283,7 +283,6 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc) { struct kernfs_super_info *info = kernfs_info(sb); - struct kernfs_root *kf_root = kfc->root; struct inode *inode; struct dentry *root;
@@ -304,9 +303,7 @@ static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *k sb->s_shrink->seeks = 0; /* get root inode, initialize and unlock it */ - down_read(&kf_root->kernfs_rwsem); inode = kernfs_get_inode(sb, info->root->kn); - up_read(&kf_root->kernfs_rwsem); if (!inode) { pr_debug("kernfs: could not get root inode\n"); return -ENOMEM;
--
2.56.0