From 393c3714081a53795bbff0e985d24146def6f57f Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 18 Nov 2021 15:00:08 -0800 Subject: 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 Acked-by: Tejun Heo Signed-off-by: Minchan Kim Link: https://lore.kernel.org/r/20211118230008.2679780-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/kernfs/dir.c | 110 +++++++++++++++++++++++++++++++--------------------- fs/kernfs/file.c | 6 ++- fs/kernfs/inode.c | 22 +++++++---- fs/kernfs/mount.c | 15 ++++--- fs/kernfs/symlink.c | 5 ++- 5 files changed, 95 insertions(+), 63 deletions(-) (limited to 'fs/kernfs') diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 8e0a1378a4b1..13cae0ccce74 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -17,7 +17,6 @@ #include "kernfs-internal.h" -DECLARE_RWSEM(kernfs_rwsem); static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */ static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */ static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */ @@ -26,7 +25,7 @@ static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */ static bool kernfs_active(struct kernfs_node *kn) { - lockdep_assert_held(&kernfs_rwsem); + lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem); return atomic_read(&kn->active) >= 0; } @@ -457,14 +456,15 @@ void kernfs_put_active(struct kernfs_node *kn) * return after draining is complete. */ static void kernfs_drain(struct kernfs_node *kn) - __releases(&kernfs_rwsem) __acquires(&kernfs_rwsem) + __releases(&kernfs_root(kn)->kernfs_rwsem) + __acquires(&kernfs_root(kn)->kernfs_rwsem) { struct kernfs_root *root = kernfs_root(kn); - lockdep_assert_held_write(&kernfs_rwsem); + lockdep_assert_held_write(&root->kernfs_rwsem); WARN_ON_ONCE(kernfs_active(kn)); - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); if (kernfs_lockdep(kn)) { rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_); @@ -483,7 +483,7 @@ static void kernfs_drain(struct kernfs_node *kn) kernfs_drain_open_files(kn); - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); } /** @@ -718,11 +718,12 @@ err_unlock: int kernfs_add_one(struct kernfs_node *kn) { struct kernfs_node *parent = kn->parent; + struct kernfs_root *root = kernfs_root(parent); struct kernfs_iattrs *ps_iattr; bool has_ns; int ret; - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); ret = -EINVAL; has_ns = kernfs_ns_enabled(parent); @@ -753,7 +754,7 @@ int kernfs_add_one(struct kernfs_node *kn) ps_iattr->ia_mtime = ps_iattr->ia_ctime; } - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); /* * Activate the new node unless CREATE_DEACTIVATED is requested. @@ -767,7 +768,7 @@ int kernfs_add_one(struct kernfs_node *kn) return 0; out_unlock: - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); return ret; } @@ -788,7 +789,7 @@ static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent, bool has_ns = kernfs_ns_enabled(parent); unsigned int hash; - lockdep_assert_held(&kernfs_rwsem); + lockdep_assert_held(&kernfs_root(parent)->kernfs_rwsem); if (has_ns != (bool)ns) { WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n", @@ -820,7 +821,7 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent, size_t len; char *p, *name; - lockdep_assert_held_read(&kernfs_rwsem); + lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem); /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */ spin_lock_irq(&kernfs_rename_lock); @@ -859,11 +860,12 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name, const void *ns) { struct kernfs_node *kn; + struct kernfs_root *root = kernfs_root(parent); - down_read(&kernfs_rwsem); + down_read(&root->kernfs_rwsem); kn = kernfs_find_ns(parent, name, ns); kernfs_get(kn); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return kn; } @@ -883,11 +885,12 @@ struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path, const void *ns) { struct kernfs_node *kn; + struct kernfs_root *root = kernfs_root(parent); - down_read(&kernfs_rwsem); + down_read(&root->kernfs_rwsem); kn = kernfs_walk_ns(parent, path, ns); kernfs_get(kn); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return kn; } @@ -912,6 +915,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, return ERR_PTR(-ENOMEM); idr_init(&root->ino_idr); + init_rwsem(&root->kernfs_rwsem); INIT_LIST_HEAD(&root->supers); /* @@ -1035,6 +1039,7 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent, static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags) { struct kernfs_node *kn; + struct kernfs_root *root; if (flags & LOOKUP_RCU) return -ECHILD; @@ -1046,18 +1051,19 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags) /* If the kernfs parent node has changed discard and * proceed to ->lookup. */ - down_read(&kernfs_rwsem); spin_lock(&dentry->d_lock); parent = kernfs_dentry_node(dentry->d_parent); if (parent) { + spin_unlock(&dentry->d_lock); + root = kernfs_root(parent); + down_read(&root->kernfs_rwsem); if (kernfs_dir_changed(parent, dentry)) { - spin_unlock(&dentry->d_lock); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return 0; } - } - spin_unlock(&dentry->d_lock); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); + } else + spin_unlock(&dentry->d_lock); /* The kernfs parent node hasn't changed, leave the * dentry negative and return success. @@ -1066,7 +1072,8 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags) } kn = kernfs_dentry_node(dentry); - down_read(&kernfs_rwsem); + root = kernfs_root(kn); + down_read(&root->kernfs_rwsem); /* The kernfs node has been deactivated */ if (!kernfs_active(kn)) @@ -1085,10 +1092,10 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags) kernfs_info(dentry->d_sb)->ns != kn->ns) goto out_bad; - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return 1; out_bad: - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return 0; } @@ -1102,10 +1109,12 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir, { struct kernfs_node *parent = dir->i_private; struct kernfs_node *kn; + struct kernfs_root *root; struct inode *inode = NULL; const void *ns = NULL; - down_read(&kernfs_rwsem); + root = kernfs_root(parent); + down_read(&root->kernfs_rwsem); if (kernfs_ns_enabled(parent)) ns = kernfs_info(dir->i_sb)->ns; @@ -1116,7 +1125,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir, * create a negative. */ if (!kernfs_active(kn)) { - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); return NULL; } inode = kernfs_get_inode(dir->i_sb, kn); @@ -1131,7 +1140,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir, */ if (!IS_ERR(inode)) kernfs_set_rev(parent, dentry); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); /* instantiate and hash (possibly negative) dentry */ return d_splice_alias(inode, dentry); @@ -1254,7 +1263,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos, { struct rb_node *rbn; - lockdep_assert_held_write(&kernfs_rwsem); + lockdep_assert_held_write(&kernfs_root(root)->kernfs_rwsem); /* if first iteration, visit leftmost descendant which may be root */ if (!pos) @@ -1289,8 +1298,9 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos, void kernfs_activate(struct kernfs_node *kn) { struct kernfs_node *pos; + struct kernfs_root *root = kernfs_root(kn); - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); pos = NULL; while ((pos = kernfs_next_descendant_post(pos, kn))) { @@ -1304,14 +1314,14 @@ void kernfs_activate(struct kernfs_node *kn) pos->flags |= KERNFS_ACTIVATED; } - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); } static void __kernfs_remove(struct kernfs_node *kn) { struct kernfs_node *pos; - lockdep_assert_held_write(&kernfs_rwsem); + lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem); /* * Short-circuit if non-root @kn has already finished removal. @@ -1381,9 +1391,11 @@ static void __kernfs_remove(struct kernfs_node *kn) */ void kernfs_remove(struct kernfs_node *kn) { - down_write(&kernfs_rwsem); + struct kernfs_root *root = kernfs_root(kn); + + down_write(&root->kernfs_rwsem); __kernfs_remove(kn); - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); } /** @@ -1469,8 +1481,9 @@ void kernfs_unbreak_active_protection(struct kernfs_node *kn) bool kernfs_remove_self(struct kernfs_node *kn) { bool ret; + struct kernfs_root *root = kernfs_root(kn); - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); kernfs_break_active_protection(kn); /* @@ -1498,9 +1511,9 @@ bool kernfs_remove_self(struct kernfs_node *kn) atomic_read(&kn->active) == KN_DEACTIVATED_BIAS) break; - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); schedule(); - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); } finish_wait(waitq, &wait); WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb)); @@ -1513,7 +1526,7 @@ bool kernfs_remove_self(struct kernfs_node *kn) */ kernfs_unbreak_active_protection(kn); - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); return ret; } @@ -1530,6 +1543,7 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name, const void *ns) { struct kernfs_node *kn; + struct kernfs_root *root; if (!parent) { WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n", @@ -1537,13 +1551,14 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name, return -ENOENT; } - down_write(&kernfs_rwsem); + root = kernfs_root(parent); + down_write(&root->kernfs_rwsem); kn = kernfs_find_ns(parent, name, ns); if (kn) __kernfs_remove(kn); - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); if (kn) return 0; @@ -1562,6 +1577,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, const char *new_name, const void *new_ns) { struct kernfs_node *old_parent; + struct kernfs_root *root; const char *old_name = NULL; int error; @@ -1569,7 +1585,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, if (!kn->parent) return -EINVAL; - down_write(&kernfs_rwsem); + root = kernfs_root(kn); + down_write(&root->kernfs_rwsem); error = -ENOENT; if (!kernfs_active(kn) || !kernfs_active(new_parent) || @@ -1623,7 +1640,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, error = 0; out: - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); return error; } @@ -1694,11 +1711,14 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) struct dentry *dentry = file->f_path.dentry; struct kernfs_node *parent = kernfs_dentry_node(dentry); struct kernfs_node *pos = file->private_data; + struct kernfs_root *root; const void *ns = NULL; if (!dir_emit_dots(file, ctx)) return 0; - down_read(&kernfs_rwsem); + + root = kernfs_root(parent); + down_read(&root->kernfs_rwsem); if (kernfs_ns_enabled(parent)) ns = kernfs_info(dentry->d_sb)->ns; @@ -1715,12 +1735,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) file->private_data = pos; kernfs_get(pos); - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); if (!dir_emit(ctx, name, len, ino, type)) return 0; - down_read(&kernfs_rwsem); + down_read(&root->kernfs_rwsem); } - up_read(&kernfs_rwsem); + up_read(&root->kernfs_rwsem); file->private_data = NULL; ctx->pos = INT_MAX; return 0; diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 60e2a86c535e..9414a7a60a9f 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -847,6 +847,7 @@ static void kernfs_notify_workfn(struct work_struct *work) { struct kernfs_node *kn; struct kernfs_super_info *info; + struct kernfs_root *root; repeat: /* pop one off the notify_list */ spin_lock_irq(&kernfs_notify_lock); @@ -859,8 +860,9 @@ repeat: kn->attr.notify_next = NULL; spin_unlock_irq(&kernfs_notify_lock); + root = kernfs_root(kn); /* kick fsnotify */ - down_write(&kernfs_rwsem); + down_write(&root->kernfs_rwsem); list_for_each_entry(info, &kernfs_root(kn)->supers, node) { struct kernfs_node *parent; @@ -898,7 +900,7 @@ repeat: iput(inode); } - up_write(&kernfs_rwsem); + up_write(&root->kernfs_rwsem); kernfs_put(kn); goto repeat; } diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index c0eae1725435..3d783d80f5da 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -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; } diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index f2f909d09f52..cfa79715fc1a 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -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 diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c index 19a6c71c6ff5..0ab13824822f 100644 --- a/fs/kernfs/symlink.c +++ b/fs/kernfs/symlink.c @@ -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; } -- cgit v1.2.3-58-ga151