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kernfs: change kernfs_rename_lock into a read-write lock.

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kernfs_rename_lock protects a node's ->parent and thus kernfs topology.
Thus it can be used in cases that rely on a stable kernfs topology.
Change it to a read-write lock for better scalability.

Suggested by: Al Viro <viro@zeniv.linux.org.uk>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Link: https://lore.kernel.org/r/20230309110932.2889010-4-imran.f.khan@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Imran Khan 2023-03-09 22:09:32 +11:00 committed by Greg Kroah-Hartman
parent c9f2dfb7b5
commit 06fb473613
1 changed files with 9 additions and 9 deletions
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18
fs/kernfs/dir.c
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@ -17,7 +17,7 @@
#include "kernfs-internal.h"
static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
static DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */
/*
* Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
* call pr_cont() while holding rename_lock. Because sometimes pr_cont()
@ -196,9 +196,9 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
unsigned long flags;
int ret;
spin_lock_irqsave(&kernfs_rename_lock, flags);
read_lock_irqsave(&kernfs_rename_lock, flags);
ret = kernfs_name_locked(kn, buf, buflen);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
read_unlock_irqrestore(&kernfs_rename_lock, flags);
return ret;
}
@ -224,9 +224,9 @@ int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
unsigned long flags;
int ret;
spin_lock_irqsave(&kernfs_rename_lock, flags);
read_lock_irqsave(&kernfs_rename_lock, flags);
ret = kernfs_path_from_node_locked(to, from, buf, buflen);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
read_unlock_irqrestore(&kernfs_rename_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kernfs_path_from_node);
@ -294,10 +294,10 @@ struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
struct kernfs_node *parent;
unsigned long flags;
spin_lock_irqsave(&kernfs_rename_lock, flags);
read_lock_irqsave(&kernfs_rename_lock, flags);
parent = kn->parent;
kernfs_get(parent);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
read_unlock_irqrestore(&kernfs_rename_lock, flags);
return parent;
}
@ -1731,7 +1731,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
kernfs_get(new_parent);
/* rename_lock protects ->parent and ->name accessors */
spin_lock_irq(&kernfs_rename_lock);
write_lock_irq(&kernfs_rename_lock);
old_parent = kn->parent;
kn->parent = new_parent;
@ -1742,7 +1742,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
kn->name = new_name;
}
spin_unlock_irq(&kernfs_rename_lock);
write_unlock_irq(&kernfs_rename_lock);
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kernfs_link_sibling(kn);