fsnotify: srcu to protect read side of inode and vfsmount locks
Currently reading the inode->i_fsnotify_marks or vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the read and the write side. This patch protects the read side of those lists with a new single srcu. Signed-off-by: Eric Paris <eparis@redhat.com>
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@@ -85,10 +85,12 @@
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/kthread.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/srcu.h>
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#include <linux/writeback.h> /* for inode_lock */
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#include <asm/atomic.h>
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@@ -96,6 +98,11 @@
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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struct srcu_struct fsnotify_mark_srcu;
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static DEFINE_SPINLOCK(destroy_lock);
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static LIST_HEAD(destroy_list);
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static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
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void fsnotify_get_mark(struct fsnotify_mark *mark)
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{
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atomic_inc(&mark->refcnt);
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@@ -144,11 +151,14 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
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list_del_init(&mark->g_list);
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fsnotify_put_mark(mark); /* for i_list and g_list */
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spin_unlock(&group->mark_lock);
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spin_unlock(&mark->lock);
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spin_lock(&destroy_lock);
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list_add(&mark->destroy_list, &destroy_list);
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spin_unlock(&destroy_lock);
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wake_up(&destroy_waitq);
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/*
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* Some groups like to know that marks are being freed. This is a
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* callback to the group function to let it know that this mark
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@@ -263,12 +273,17 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
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err:
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mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
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list_del_init(&mark->g_list);
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mark->group = NULL;
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atomic_dec(&group->num_marks);
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fsnotify_put_mark(mark);
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spin_unlock(&group->mark_lock);
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spin_unlock(&mark->lock);
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spin_lock(&destroy_lock);
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list_add(&mark->destroy_list, &destroy_list);
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spin_unlock(&destroy_lock);
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wake_up(&destroy_waitq);
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return ret;
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}
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@@ -326,3 +341,42 @@ void fsnotify_init_mark(struct fsnotify_mark *mark,
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atomic_set(&mark->refcnt, 1);
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mark->free_mark = free_mark;
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}
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static int fsnotify_mark_destroy(void *ignored)
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{
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struct fsnotify_mark *mark, *next;
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LIST_HEAD(private_destroy_list);
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for (;;) {
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spin_lock(&destroy_lock);
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list_for_each_entry_safe(mark, next, &destroy_list, destroy_list) {
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list_del(&mark->destroy_list);
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list_add(&mark->destroy_list, &private_destroy_list);
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}
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spin_unlock(&destroy_lock);
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synchronize_srcu(&fsnotify_mark_srcu);
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list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
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list_del_init(&mark->destroy_list);
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fsnotify_put_mark(mark);
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}
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wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
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}
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return 0;
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}
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static int __init fsnotify_mark_init(void)
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{
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struct task_struct *thread;
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thread = kthread_run(fsnotify_mark_destroy, NULL,
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"fsnotify_mark");
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if (IS_ERR(thread))
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panic("unable to start fsnotify mark destruction thread.");
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return 0;
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}
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device_initcall(fsnotify_mark_init);
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