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authorGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-13 14:49:01 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-13 14:49:01 -0800
commit683bb2761fbf123b24aed03a1c0d5d7556ec3018 (patch)
treef6bb7a039fa1bf9387f70dfef9bec5474178547c /fs/kernfs
parent87da149343c8c93f6984c0f4b9da7651709624f7 (diff)
Revert "kernfs: fix get_active failure handling in kernfs_seq_*()"
This reverts commit d92d2e6bd72b653f9811e0c9c46307c743b3fc58. Tejun writes: I'm sorry but can you please revert the whole series? get_active() waiting while a node is deactivated has potential to lead to deadlock and that deactivate/reactivate interface is something fundamentally flawed and that cgroup will have to work with the remove_self() like everybody else. IOW, I think the first posting was correct. Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/kernfs')
-rw-r--r--fs/kernfs/file.c51
1 files changed, 7 insertions, 44 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index bdd38854ef65..316604cc3a1c 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -54,38 +54,6 @@ static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
return kn->attr.ops;
}
-/*
- * As kernfs_seq_stop() is also called after kernfs_seq_start() or
- * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
- * a seq_file iteration which is fully initialized with an active reference
- * or an aborted kernfs_seq_start() due to get_active failure. The
- * position pointer is the only context for each seq_file iteration and
- * thus the stop condition should be encoded in it. As the return value is
- * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
- * choice to indicate get_active failure.
- *
- * Unfortunately, this is complicated due to the optional custom seq_file
- * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
- * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
- * custom seq_file operations and thus can't decide whether put_active
- * should be performed or not only on ERR_PTR(-ENODEV).
- *
- * This is worked around by factoring out the custom seq_stop() and
- * put_active part into kernfs_seq_stop_active(), skipping it from
- * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
- * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
- * that kernfs_seq_stop_active() is skipped only after get_active failure.
- */
-static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
-{
- struct kernfs_open_file *of = sf->private;
- const struct kernfs_ops *ops = kernfs_ops(of->kn);
-
- if (ops->seq_stop)
- ops->seq_stop(sf, v);
- kernfs_put_active(of->kn);
-}
-
static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
{
struct kernfs_open_file *of = sf->private;
@@ -101,11 +69,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
ops = kernfs_ops(of->kn);
if (ops->seq_start) {
- void *next = ops->seq_start(sf, ppos);
- /* see the comment above kernfs_seq_stop_active() */
- if (next == ERR_PTR(-ENODEV))
- kernfs_seq_stop_active(sf, next);
- return next;
+ return ops->seq_start(sf, ppos);
} else {
/*
* The same behavior and code as single_open(). Returns
@@ -121,11 +85,7 @@ static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
const struct kernfs_ops *ops = kernfs_ops(of->kn);
if (ops->seq_next) {
- void *next = ops->seq_next(sf, v, ppos);
- /* see the comment above kernfs_seq_stop_active() */
- if (next == ERR_PTR(-ENODEV))
- kernfs_seq_stop_active(sf, next);
- return next;
+ return ops->seq_next(sf, v, ppos);
} else {
/*
* The same behavior and code as single_open(), always
@@ -139,9 +99,12 @@ static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
static void kernfs_seq_stop(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
+ const struct kernfs_ops *ops = kernfs_ops(of->kn);
- if (v != ERR_PTR(-ENODEV))
- kernfs_seq_stop_active(sf, v);
+ if (ops->seq_stop)
+ ops->seq_stop(sf, v);
+
+ kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
}