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configfs: provide exclusion between IO and removals

Forráskód böngészése 
Make sure that attribute methods are not called after the item
has been removed from the tree.  To do so, we
	* at the point of no return in removals, grab ->frag_sem
exclusive and mark the fragment dead.
	* call the methods of attributes with ->frag_sem taken
shared and only after having verified that the fragment is still
alive.

	The main benefit is for method instances - they are
guaranteed that the objects they are accessing *and* all ancestors
are still there.  Another win is that we don't need to bother
with extra refcount on config_item when opening a file -
the item will be alive for as long as it stays in the tree, and
we won't touch it/attributes/any associated data after it's
been removed from the tree.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Al Viro
2019-08-31 09:43:43 +02:00
committed by Christoph Hellwig
szülő 47320fbe11
commit b0841eefd9
2 fájl változott, egészen pontosan 81 új sor hozzáadva és 19 régi sor törölve
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23
fs/configfs/dir.c
Fájl megtekintése

@@ -1461,6 +1461,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
struct config_item *item;
struct configfs_subsystem *subsys;
struct configfs_dirent *sd;
struct configfs_fragment *frag;
struct module *subsys_owner = NULL, *dead_item_owner = NULL;
int ret;
@@ -1518,6 +1519,16 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
}
} while (ret == -EAGAIN);
frag = sd->s_frag;
if (down_write_killable(&frag->frag_sem)) {
spin_lock(&configfs_dirent_lock);
configfs_detach_rollback(dentry);
spin_unlock(&configfs_dirent_lock);
return -EINTR;
}
frag->frag_dead = true;
up_write(&frag->frag_sem);
/* Get a working ref for the duration of this function */
item = configfs_get_config_item(dentry);
@@ -1821,6 +1832,12 @@ void configfs_unregister_group(struct config_group *group)
struct configfs_subsystem *subsys = group->cg_subsys;
struct dentry *dentry = group->cg_item.ci_dentry;
struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
struct configfs_dirent *sd = dentry->d_fsdata;
struct configfs_fragment *frag = sd->s_frag;
down_write(&frag->frag_sem);
frag->frag_dead = true;
up_write(&frag->frag_sem);
inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
spin_lock(&configfs_dirent_lock);
@@ -1947,12 +1964,18 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
struct config_group *group = &subsys->su_group;
struct dentry *dentry = group->cg_item.ci_dentry;
struct dentry *root = dentry->d_sb->s_root;
struct configfs_dirent *sd = dentry->d_fsdata;
struct configfs_fragment *frag = sd->s_frag;
if (dentry->d_parent != root) {
pr_err("Tried to unregister non-subsystem!\n");
return;
}
down_write(&frag->frag_sem);
frag->frag_dead = true;
up_write(&frag->frag_sem);
inode_lock_nested(d_inode(root),
I_MUTEX_PARENT);
inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);