kernfs: switch global kernfs_rwsem lock to per-fs lock
The kernfs implementation has big lock granularity(kernfs_rwsem) so every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock. It makes trouble for some cases to wait the global lock for a long time even though they are totally independent contexts each other. A general example is process A goes under direct reclaim with holding the lock when it accessed the file in sysfs and process B is waiting the lock with exclusive mode and then process C is waiting the lock until process B could finish the job after it gets the lock from process A. This patch switches the global kernfs_rwsem to per-fs lock, which put the rwsem into kernfs_root. Suggested-by: Tejun Heo <tj@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> Link: https://lore.kernel.org/r/20211118230008.2679780-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Minchan Kim
Greg Kroah-Hartman
parent
1360572566
commit
393c371408
110
fs/kernfs/dir.c
110
fs/kernfs/dir.c
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@ -17,7 +17,6 @@
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#include "kernfs-internal.h"
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DECLARE_RWSEM(kernfs_rwsem);
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static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
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static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
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static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
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@ -26,7 +25,7 @@ static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
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static bool kernfs_active(struct kernfs_node *kn)
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{
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lockdep_assert_held(&kernfs_rwsem);
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lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
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return atomic_read(&kn->active) >= 0;
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}
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@ -457,14 +456,15 @@ void kernfs_put_active(struct kernfs_node *kn)
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* return after draining is complete.
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*/
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static void kernfs_drain(struct kernfs_node *kn)
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__releases(&kernfs_rwsem) __acquires(&kernfs_rwsem)
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__releases(&kernfs_root(kn)->kernfs_rwsem)
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__acquires(&kernfs_root(kn)->kernfs_rwsem)
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{
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struct kernfs_root *root = kernfs_root(kn);
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lockdep_assert_held_write(&kernfs_rwsem);
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lockdep_assert_held_write(&root->kernfs_rwsem);
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WARN_ON_ONCE(kernfs_active(kn));
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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if (kernfs_lockdep(kn)) {
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rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
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@ -483,7 +483,7 @@ static void kernfs_drain(struct kernfs_node *kn)
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kernfs_drain_open_files(kn);
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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}
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/**
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@ -718,11 +718,12 @@ err_unlock:
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int kernfs_add_one(struct kernfs_node *kn)
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{
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struct kernfs_node *parent = kn->parent;
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struct kernfs_root *root = kernfs_root(parent);
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struct kernfs_iattrs *ps_iattr;
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bool has_ns;
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int ret;
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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ret = -EINVAL;
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has_ns = kernfs_ns_enabled(parent);
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@ -753,7 +754,7 @@ int kernfs_add_one(struct kernfs_node *kn)
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ps_iattr->ia_mtime = ps_iattr->ia_ctime;
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}
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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/*
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* Activate the new node unless CREATE_DEACTIVATED is requested.
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@ -767,7 +768,7 @@ int kernfs_add_one(struct kernfs_node *kn)
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return 0;
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out_unlock:
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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return ret;
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}
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@ -788,7 +789,7 @@ static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
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bool has_ns = kernfs_ns_enabled(parent);
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unsigned int hash;
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lockdep_assert_held(&kernfs_rwsem);
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lockdep_assert_held(&kernfs_root(parent)->kernfs_rwsem);
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if (has_ns != (bool)ns) {
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WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
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@ -820,7 +821,7 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
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size_t len;
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char *p, *name;
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lockdep_assert_held_read(&kernfs_rwsem);
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lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
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/* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
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spin_lock_irq(&kernfs_rename_lock);
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@ -859,11 +860,12 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
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const char *name, const void *ns)
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{
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struct kernfs_node *kn;
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struct kernfs_root *root = kernfs_root(parent);
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down_read(&kernfs_rwsem);
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down_read(&root->kernfs_rwsem);
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kn = kernfs_find_ns(parent, name, ns);
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kernfs_get(kn);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return kn;
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}
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@ -883,11 +885,12 @@ struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
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const char *path, const void *ns)
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{
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struct kernfs_node *kn;
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struct kernfs_root *root = kernfs_root(parent);
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down_read(&kernfs_rwsem);
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down_read(&root->kernfs_rwsem);
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kn = kernfs_walk_ns(parent, path, ns);
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kernfs_get(kn);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return kn;
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}
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@ -912,6 +915,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
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return ERR_PTR(-ENOMEM);
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idr_init(&root->ino_idr);
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init_rwsem(&root->kernfs_rwsem);
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INIT_LIST_HEAD(&root->supers);
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/*
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@ -1035,6 +1039,7 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
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static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct kernfs_node *kn;
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struct kernfs_root *root;
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if (flags & LOOKUP_RCU)
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return -ECHILD;
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@ -1046,18 +1051,19 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
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/* If the kernfs parent node has changed discard and
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* proceed to ->lookup.
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*/
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down_read(&kernfs_rwsem);
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spin_lock(&dentry->d_lock);
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parent = kernfs_dentry_node(dentry->d_parent);
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if (parent) {
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spin_unlock(&dentry->d_lock);
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root = kernfs_root(parent);
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down_read(&root->kernfs_rwsem);
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if (kernfs_dir_changed(parent, dentry)) {
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spin_unlock(&dentry->d_lock);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return 0;
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}
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}
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spin_unlock(&dentry->d_lock);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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} else
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spin_unlock(&dentry->d_lock);
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/* The kernfs parent node hasn't changed, leave the
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* dentry negative and return success.
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@ -1066,7 +1072,8 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
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}
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kn = kernfs_dentry_node(dentry);
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down_read(&kernfs_rwsem);
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root = kernfs_root(kn);
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down_read(&root->kernfs_rwsem);
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/* The kernfs node has been deactivated */
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if (!kernfs_active(kn))
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@ -1085,10 +1092,10 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
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kernfs_info(dentry->d_sb)->ns != kn->ns)
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goto out_bad;
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return 1;
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out_bad:
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return 0;
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}
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@ -1102,10 +1109,12 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
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{
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struct kernfs_node *parent = dir->i_private;
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struct kernfs_node *kn;
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struct kernfs_root *root;
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struct inode *inode = NULL;
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const void *ns = NULL;
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down_read(&kernfs_rwsem);
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root = kernfs_root(parent);
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down_read(&root->kernfs_rwsem);
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if (kernfs_ns_enabled(parent))
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ns = kernfs_info(dir->i_sb)->ns;
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@ -1116,7 +1125,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
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* create a negative.
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*/
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if (!kernfs_active(kn)) {
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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return NULL;
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}
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inode = kernfs_get_inode(dir->i_sb, kn);
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@ -1131,7 +1140,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
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*/
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if (!IS_ERR(inode))
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kernfs_set_rev(parent, dentry);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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/* instantiate and hash (possibly negative) dentry */
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return d_splice_alias(inode, dentry);
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@ -1254,7 +1263,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
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{
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struct rb_node *rbn;
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lockdep_assert_held_write(&kernfs_rwsem);
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lockdep_assert_held_write(&kernfs_root(root)->kernfs_rwsem);
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/* if first iteration, visit leftmost descendant which may be root */
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if (!pos)
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@ -1289,8 +1298,9 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
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void kernfs_activate(struct kernfs_node *kn)
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{
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struct kernfs_node *pos;
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struct kernfs_root *root = kernfs_root(kn);
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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pos = NULL;
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while ((pos = kernfs_next_descendant_post(pos, kn))) {
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@ -1304,14 +1314,14 @@ void kernfs_activate(struct kernfs_node *kn)
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pos->flags |= KERNFS_ACTIVATED;
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}
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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}
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static void __kernfs_remove(struct kernfs_node *kn)
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{
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struct kernfs_node *pos;
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lockdep_assert_held_write(&kernfs_rwsem);
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lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
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/*
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* Short-circuit if non-root @kn has already finished removal.
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@ -1381,9 +1391,11 @@ static void __kernfs_remove(struct kernfs_node *kn)
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*/
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void kernfs_remove(struct kernfs_node *kn)
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{
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down_write(&kernfs_rwsem);
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struct kernfs_root *root = kernfs_root(kn);
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down_write(&root->kernfs_rwsem);
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__kernfs_remove(kn);
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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}
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/**
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@ -1469,8 +1481,9 @@ void kernfs_unbreak_active_protection(struct kernfs_node *kn)
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bool kernfs_remove_self(struct kernfs_node *kn)
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{
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bool ret;
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struct kernfs_root *root = kernfs_root(kn);
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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kernfs_break_active_protection(kn);
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/*
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@ -1498,9 +1511,9 @@ bool kernfs_remove_self(struct kernfs_node *kn)
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atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
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break;
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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schedule();
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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}
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finish_wait(waitq, &wait);
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WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
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@ -1513,7 +1526,7 @@ bool kernfs_remove_self(struct kernfs_node *kn)
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*/
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kernfs_unbreak_active_protection(kn);
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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return ret;
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}
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@ -1530,6 +1543,7 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
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const void *ns)
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{
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struct kernfs_node *kn;
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struct kernfs_root *root;
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if (!parent) {
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WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
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@ -1537,13 +1551,14 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
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return -ENOENT;
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}
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down_write(&kernfs_rwsem);
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root = kernfs_root(parent);
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down_write(&root->kernfs_rwsem);
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kn = kernfs_find_ns(parent, name, ns);
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if (kn)
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__kernfs_remove(kn);
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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if (kn)
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return 0;
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@ -1562,6 +1577,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
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const char *new_name, const void *new_ns)
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{
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struct kernfs_node *old_parent;
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struct kernfs_root *root;
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const char *old_name = NULL;
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int error;
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@ -1569,7 +1585,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
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if (!kn->parent)
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return -EINVAL;
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down_write(&kernfs_rwsem);
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root = kernfs_root(kn);
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down_write(&root->kernfs_rwsem);
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error = -ENOENT;
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if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
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@ -1623,7 +1640,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
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error = 0;
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out:
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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return error;
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}
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@ -1694,11 +1711,14 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
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struct dentry *dentry = file->f_path.dentry;
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struct kernfs_node *parent = kernfs_dentry_node(dentry);
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struct kernfs_node *pos = file->private_data;
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struct kernfs_root *root;
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const void *ns = NULL;
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if (!dir_emit_dots(file, ctx))
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return 0;
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down_read(&kernfs_rwsem);
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root = kernfs_root(parent);
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down_read(&root->kernfs_rwsem);
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if (kernfs_ns_enabled(parent))
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ns = kernfs_info(dentry->d_sb)->ns;
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@ -1715,12 +1735,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
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file->private_data = pos;
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kernfs_get(pos);
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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if (!dir_emit(ctx, name, len, ino, type))
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return 0;
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down_read(&kernfs_rwsem);
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down_read(&root->kernfs_rwsem);
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}
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up_read(&kernfs_rwsem);
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up_read(&root->kernfs_rwsem);
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file->private_data = NULL;
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ctx->pos = INT_MAX;
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return 0;
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@ -847,6 +847,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
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{
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struct kernfs_node *kn;
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struct kernfs_super_info *info;
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struct kernfs_root *root;
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repeat:
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/* pop one off the notify_list */
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spin_lock_irq(&kernfs_notify_lock);
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@ -859,8 +860,9 @@ repeat:
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kn->attr.notify_next = NULL;
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spin_unlock_irq(&kernfs_notify_lock);
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root = kernfs_root(kn);
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/* kick fsnotify */
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down_write(&kernfs_rwsem);
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down_write(&root->kernfs_rwsem);
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list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
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struct kernfs_node *parent;
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@ -898,7 +900,7 @@ repeat:
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iput(inode);
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}
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up_write(&kernfs_rwsem);
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up_write(&root->kernfs_rwsem);
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kernfs_put(kn);
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goto repeat;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -99,10 +99,11 @@ int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
|
|||
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
|
||||
{
|
||||
int ret;
|
||||
struct kernfs_root *root = kernfs_root(kn);
|
||||
|
||||
down_write(&kernfs_rwsem);
|
||||
down_write(&root->kernfs_rwsem);
|
||||
ret = __kernfs_setattr(kn, iattr);
|
||||
up_write(&kernfs_rwsem);
|
||||
up_write(&root->kernfs_rwsem);
|
||||
return ret;
|
||||
}
|
||||
|
||||
|
|
@ -111,12 +112,14 @@ int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
|
|||
{
|
||||
struct inode *inode = d_inode(dentry);
|
||||
struct kernfs_node *kn = inode->i_private;
|
||||
struct kernfs_root *root;
|
||||
int error;
|
||||
|
||||
if (!kn)
|
||||
return -EINVAL;
|
||||
|
||||
down_write(&kernfs_rwsem);
|
||||
root = kernfs_root(kn);
|
||||
down_write(&root->kernfs_rwsem);
|
||||
error = setattr_prepare(&init_user_ns, dentry, iattr);
|
||||
if (error)
|
||||
goto out;
|
||||
|
|
@ -129,7 +132,7 @@ int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
|
|||
setattr_copy(&init_user_ns, inode, iattr);
|
||||
|
||||
out:
|
||||
up_write(&kernfs_rwsem);
|
||||
up_write(&root->kernfs_rwsem);
|
||||
return error;
|
||||
}
|
||||
|
||||
|
|
@ -184,13 +187,14 @@ int kernfs_iop_getattr(struct user_namespace *mnt_userns,
|
|||
{
|
||||
struct inode *inode = d_inode(path->dentry);
|
||||
struct kernfs_node *kn = inode->i_private;
|
||||
struct kernfs_root *root = kernfs_root(kn);
|
||||
|
||||
down_read(&kernfs_rwsem);
|
||||
down_read(&root->kernfs_rwsem);
|
||||
spin_lock(&inode->i_lock);
|
||||
kernfs_refresh_inode(kn, inode);
|
||||
generic_fillattr(&init_user_ns, inode, stat);
|
||||
spin_unlock(&inode->i_lock);
|
||||
up_read(&kernfs_rwsem);
|
||||
up_read(&root->kernfs_rwsem);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -274,19 +278,21 @@ int kernfs_iop_permission(struct user_namespace *mnt_userns,
|
|||
struct inode *inode, int mask)
|
||||
{
|
||||
struct kernfs_node *kn;
|
||||
struct kernfs_root *root;
|
||||
int ret;
|
||||
|
||||
if (mask & MAY_NOT_BLOCK)
|
||||
return -ECHILD;
|
||||
|
||||
kn = inode->i_private;
|
||||
root = kernfs_root(kn);
|
||||
|
||||
down_read(&kernfs_rwsem);
|
||||
down_read(&root->kernfs_rwsem);
|
||||
spin_lock(&inode->i_lock);
|
||||
kernfs_refresh_inode(kn, inode);
|
||||
ret = generic_permission(&init_user_ns, inode, mask);
|
||||
spin_unlock(&inode->i_lock);
|
||||
up_read(&kernfs_rwsem);
|
||||
up_read(&root->kernfs_rwsem);
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -236,6 +236,7 @@ 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;
|
||||
|
||||
|
|
@ -255,9 +256,9 @@ 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(&kernfs_rwsem);
|
||||
down_read(&kf_root->kernfs_rwsem);
|
||||
inode = kernfs_get_inode(sb, info->root->kn);
|
||||
up_read(&kernfs_rwsem);
|
||||
up_read(&kf_root->kernfs_rwsem);
|
||||
if (!inode) {
|
||||
pr_debug("kernfs: could not get root inode\n");
|
||||
return -ENOMEM;
|
||||
|
|
@ -334,6 +335,7 @@ int kernfs_get_tree(struct fs_context *fc)
|
|||
|
||||
if (!sb->s_root) {
|
||||
struct kernfs_super_info *info = kernfs_info(sb);
|
||||
struct kernfs_root *root = kfc->root;
|
||||
|
||||
kfc->new_sb_created = true;
|
||||
|
||||
|
|
@ -344,9 +346,9 @@ int kernfs_get_tree(struct fs_context *fc)
|
|||
}
|
||||
sb->s_flags |= SB_ACTIVE;
|
||||
|
||||
down_write(&kernfs_rwsem);
|
||||
down_write(&root->kernfs_rwsem);
|
||||
list_add(&info->node, &info->root->supers);
|
||||
up_write(&kernfs_rwsem);
|
||||
up_write(&root->kernfs_rwsem);
|
||||
}
|
||||
|
||||
fc->root = dget(sb->s_root);
|
||||
|
|
@ -371,10 +373,11 @@ void kernfs_free_fs_context(struct fs_context *fc)
|
|||
void kernfs_kill_sb(struct super_block *sb)
|
||||
{
|
||||
struct kernfs_super_info *info = kernfs_info(sb);
|
||||
struct kernfs_root *root = info->root;
|
||||
|
||||
down_write(&kernfs_rwsem);
|
||||
down_write(&root->kernfs_rwsem);
|
||||
list_del(&info->node);
|
||||
up_write(&kernfs_rwsem);
|
||||
up_write(&root->kernfs_rwsem);
|
||||
|
||||
/*
|
||||
* Remove the superblock from fs_supers/s_instances
|
||||
|
|
|
|||
|
|
@ -113,11 +113,12 @@ static int kernfs_getlink(struct inode *inode, char *path)
|
|||
struct kernfs_node *kn = inode->i_private;
|
||||
struct kernfs_node *parent = kn->parent;
|
||||
struct kernfs_node *target = kn->symlink.target_kn;
|
||||
struct kernfs_root *root = kernfs_root(parent);
|
||||
int error;
|
||||
|
||||
down_read(&kernfs_rwsem);
|
||||
down_read(&root->kernfs_rwsem);
|
||||
error = kernfs_get_target_path(parent, target, path);
|
||||
up_read(&kernfs_rwsem);
|
||||
up_read(&root->kernfs_rwsem);
|
||||
|
||||
return error;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -16,6 +16,7 @@
|
|||
#include <linux/atomic.h>
|
||||
#include <linux/uidgid.h>
|
||||
#include <linux/wait.h>
|
||||
#include <linux/rwsem.h>
|
||||
|
||||
struct file;
|
||||
struct dentry;
|
||||
|
|
@ -197,6 +198,7 @@ struct kernfs_root {
|
|||
struct list_head supers;
|
||||
|
||||
wait_queue_head_t deactivate_waitq;
|
||||
struct rw_semaphore kernfs_rwsem;
|
||||
};
|
||||
|
||||
struct kernfs_open_file {
|
||||
|
|
|
|||
Loading…
Reference in New Issue