Allow d_manage() to be called from pathwalk when it is in RCU-walk mode as well
as when it is in Ref-walk mode. This permits __follow_mount_rcu() to call
d_manage() directly. d_manage() needs a parameter to indicate that it is in
RCU-walk mode as it isn't allowed to sleep if in that mode (but should return
-ECHILD instead).
autofs4_d_manage() can then be set to retain RCU-walk mode if the daemon
accesses it and otherwise request dropping back to ref-walk mode.
Signed-off-by: David Howells <dhowe...@redhat.com>
---
Documentation/filesystems/Locking | 2 +-
Documentation/filesystems/vfs.txt | 7 ++++++-
fs/autofs4/root.c | 8 ++++++--
fs/namei.c | 14 +++++++-------
include/linux/dcache.h | 2 +-
5 files changed, 21 insertions(+), 12 deletions(-)
diff --git a/Documentation/filesystems/Locking
b/Documentation/filesystems/Locking
index 621ee98..b3b0ac4 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -31,7 +31,7 @@ d_release: no no yes
no
d_iput: no no yes no
d_dname: no no no no
d_automount: no no yes no
-d_manage: no no yes no
+d_manage: no no yes (ref-walk) maybe
--------------------------- inode_operations ---------------------------
prototypes:
diff --git a/Documentation/filesystems/vfs.txt
b/Documentation/filesystems/vfs.txt
index 3d68c2e..9bc28c2f 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -865,7 +865,7 @@ struct dentry_operations {
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
- int (*d_manage)(struct path *, bool);
+ int (*d_manage)(struct path *, bool, bool);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
@@ -960,6 +960,11 @@ struct dentry_operations {
held by the caller and the function should not initiate any mounts or
unmounts that it will then wait for.
+ If the 'rcu_walk' parameter is true, then the caller is doing a
+ pathwalk in RCU-walk mode. Sleeping is not permitted in this mode,
+ and the caller can be asked to leave it and call again by returing
+ -ECHILD.
+
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 752693f..c46d6fb 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -36,7 +36,7 @@ static long autofs4_root_compat_ioctl(struct file *,unsigned
int,unsigned long);
static int autofs4_dir_open(struct inode *inode, struct file *file);
static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct
nameidata *);
static struct vfsmount *autofs4_d_automount(struct path *);
-static int autofs4_d_manage(struct path *, bool);
+static int autofs4_d_manage(struct path *, bool, bool);
const struct file_operations autofs4_root_operations = {
.open = dcache_dir_open,
@@ -454,7 +454,7 @@ done:
return NULL;
}
-int autofs4_d_manage(struct path *path, bool mounting_here)
+int autofs4_d_manage(struct path *path, bool mounting_here, bool rcu_walk)
{
struct dentry *dentry = path->dentry;
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
@@ -469,6 +469,10 @@ int autofs4_d_manage(struct path *path, bool mounting_here)
return 0;
}
+ /* We need to sleep, so we need pathwalk to be in ref-mode */
+ if (rcu_walk)
+ return -ECHILD;
+
/* Wait for pending expires */
do_expire_wait(dentry);
diff --git a/fs/namei.c b/fs/namei.c
index c983c92..5c15daa 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -967,7 +967,7 @@ static int follow_managed(struct path *path, unsigned flags)
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
- ret = path->dentry->d_op->d_manage(path, false);
+ ret = path->dentry->d_op->d_manage(path, false, false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
@@ -1028,13 +1028,12 @@ int follow_down_one(struct path *path)
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, bool reverse_transit)
{
- unsigned abort_mask =
- reverse_transit ? 0 : DCACHE_MANAGE_TRANSIT;
-
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted;
- if (path->dentry->d_flags & abort_mask)
- return true;
+ if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
+ !reverse_transit &&
+ path->dentry->d_op->d_manage(path, false, true) < 0)
+ return false;
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted)
break;
@@ -1112,7 +1111,8 @@ int follow_down(struct path *path, bool mounting_here)
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
- ret = path->dentry->d_op->d_manage(path, mounting_here);
+ ret = path->dentry->d_op->d_manage(path, mounting_here,
+ false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 946521d..236a384 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -168,7 +168,7 @@ struct dentry_operations {
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
- int (*d_manage)(struct path *, bool);
+ int (*d_manage)(struct path *, bool, bool);
} ____cacheline_aligned;
/*
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