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Commit ab90911f authored by David Howells's avatar David Howells Committed by Al Viro
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Allow d_manage() to be used in RCU-walk mode 



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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 87556ef1

Documentation/filesystems/Locking

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ 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:

Documentation/filesystems/vfs.txt

+6 −1
Original line number Diff line number Diff line
@@ -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 dentry *, bool);

	int (*d_manage)(struct dentry *, 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.

fs/autofs4/root.c

+6 −2
Original line number Diff line number Diff line
@@ -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 dentry *, bool);

static int autofs4_d_manage(struct dentry *, bool, bool);



const struct file_operations autofs4_root_operations = {

	.open		= dcache_dir_open,
@@ -450,7 +450,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
	return NULL;

}



int autofs4_d_manage(struct dentry *dentry, bool mounting_here)

int autofs4_d_manage(struct dentry *dentry, bool mounting_here, bool rcu_walk)

{

	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
@@ -464,6 +464,10 @@ int autofs4_d_manage(struct dentry *dentry, 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);

fs/namei.c

+8 −7
Original line number Diff line number Diff line
@@ -987,7 +987,8 @@ 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->dentry, false);

			ret = path->dentry->d_op->d_manage(path->dentry,

							   false, false);

			if (ret < 0)

				return ret == -EISDIR ? 0 : ret;

		}
@@ -1048,13 +1049,12 @@ 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->dentry, false, true) < 0)

			return false;

		mounted = __lookup_mnt(path->mnt, path->dentry, 1);

		if (!mounted)

			break;
@@ -1132,7 +1132,8 @@ 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->dentry, mounting_here);

			ret = path->dentry->d_op->d_manage(

				path->dentry, mounting_here, false);

			if (ret < 0)

				return ret == -EISDIR ? 0 : ret;

		}

include/linux/dcache.h

+1 −1
Original line number Diff line number Diff line
@@ -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 dentry *, bool);

	int (*d_manage)(struct dentry *, bool, bool);

} ____cacheline_aligned;



/*