172e422ffe
In some setups directories can have many (usually negative) dentries. Hence __fsnotify_update_child_dentry_flags() function can take a significant amount of time. Since the bulk of this function happens under inode->i_lock this causes a significant contention on the lock when we remove the watch from the directory as the __fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask() races with __fsnotify_update_child_dentry_flags() calls from __fsnotify_parent() happening on children. This can lead upto softlockup reports reported by users. Fix the problem by calling fsnotify_update_children_dentry_flags() to set PARENT_WATCHED flags only when parent starts watching children. When parent stops watching children, clear false positive PARENT_WATCHED flags lazily in __fsnotify_parent() for each accessed child. Suggested-by: Jan Kara <jack@suse.cz> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com> Signed-off-by: Jan Kara <jack@suse.cz>
101 lines
2.8 KiB
C
101 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __FS_NOTIFY_FSNOTIFY_H_
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#define __FS_NOTIFY_FSNOTIFY_H_
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#include <linux/list.h>
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#include <linux/fsnotify.h>
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#include <linux/srcu.h>
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#include <linux/types.h>
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#include "../mount.h"
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/*
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* fsnotify_connp_t is what we embed in objects which connector can be attached
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* to.
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*/
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typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;
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static inline struct inode *fsnotify_conn_inode(
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struct fsnotify_mark_connector *conn)
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{
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return conn->obj;
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}
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static inline struct mount *fsnotify_conn_mount(
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struct fsnotify_mark_connector *conn)
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{
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return real_mount(conn->obj);
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}
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static inline struct super_block *fsnotify_conn_sb(
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struct fsnotify_mark_connector *conn)
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{
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return conn->obj;
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}
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static inline struct super_block *fsnotify_object_sb(void *obj,
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enum fsnotify_obj_type obj_type)
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{
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switch (obj_type) {
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case FSNOTIFY_OBJ_TYPE_INODE:
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return ((struct inode *)obj)->i_sb;
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case FSNOTIFY_OBJ_TYPE_VFSMOUNT:
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return ((struct vfsmount *)obj)->mnt_sb;
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case FSNOTIFY_OBJ_TYPE_SB:
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return (struct super_block *)obj;
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default:
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return NULL;
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}
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}
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static inline struct super_block *fsnotify_connector_sb(
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struct fsnotify_mark_connector *conn)
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{
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return fsnotify_object_sb(conn->obj, conn->type);
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}
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static inline fsnotify_connp_t *fsnotify_sb_marks(struct super_block *sb)
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{
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struct fsnotify_sb_info *sbinfo = fsnotify_sb_info(sb);
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return sbinfo ? &sbinfo->sb_marks : NULL;
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}
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/* destroy all events sitting in this groups notification queue */
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extern void fsnotify_flush_notify(struct fsnotify_group *group);
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/* protects reads of inode and vfsmount marks list */
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extern struct srcu_struct fsnotify_mark_srcu;
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/* compare two groups for sorting of marks lists */
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extern int fsnotify_compare_groups(struct fsnotify_group *a,
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struct fsnotify_group *b);
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/* Destroy all marks attached to an object via connector */
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extern void fsnotify_destroy_marks(fsnotify_connp_t *connp);
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/* run the list of all marks associated with inode and destroy them */
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static inline void fsnotify_clear_marks_by_inode(struct inode *inode)
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{
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fsnotify_destroy_marks(&inode->i_fsnotify_marks);
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}
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/* run the list of all marks associated with vfsmount and destroy them */
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static inline void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
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{
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fsnotify_destroy_marks(&real_mount(mnt)->mnt_fsnotify_marks);
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}
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/* run the list of all marks associated with sb and destroy them */
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static inline void fsnotify_clear_marks_by_sb(struct super_block *sb)
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{
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fsnotify_destroy_marks(fsnotify_sb_marks(sb));
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}
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/*
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* update the dentry->d_flags of all of inode's children to indicate if inode cares
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* about events that happen to its children.
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*/
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extern void fsnotify_set_children_dentry_flags(struct inode *inode);
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extern struct kmem_cache *fsnotify_mark_connector_cachep;
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#endif /* __FS_NOTIFY_FSNOTIFY_H_ */
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