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authorAmir Goldstein <amir73il@gmail.com>2017-06-21 15:28:32 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2017-07-04 22:03:16 +0200
commitad0af7104dadccd55cd2b390271677fac142650f (patch)
tree1e377c42709b12efc4e01507143ebba09f389bc7 /fs/overlayfs/util.c
parent04a01ac7ed3c5cd718713ef6341249a143c96b10 (diff)
vfs: introduce inode 'inuse' lock
Added an i_state flag I_INUSE and helpers to set/clear/test the bit. The 'inuse' lock is an 'advisory' inode lock, that can be used to extend exclusive create protection beyond parent->i_mutex lock among cooperating users. This is going to be used by overlayfs to get exclusive ownership on upper and work dirs among overlayfs mounts. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs/util.c')
-rw-r--r--fs/overlayfs/util.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index f093fcf2b4bd..adccd74162d6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -347,3 +347,34 @@ bool ovl_test_flag(unsigned long flag, struct inode *inode)
{
return test_bit(flag, &OVL_I(inode)->flags);
}
+
+/**
+ * Caller must hold a reference to inode to prevent it from being freed while
+ * it is marked inuse.
+ */
+bool ovl_inuse_trylock(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ bool locked = false;
+
+ spin_lock(&inode->i_lock);
+ if (!(inode->i_state & I_OVL_INUSE)) {
+ inode->i_state |= I_OVL_INUSE;
+ locked = true;
+ }
+ spin_unlock(&inode->i_lock);
+
+ return locked;
+}
+
+void ovl_inuse_unlock(struct dentry *dentry)
+{
+ if (dentry) {
+ struct inode *inode = d_inode(dentry);
+
+ spin_lock(&inode->i_lock);
+ WARN_ON(!(inode->i_state & I_OVL_INUSE));
+ inode->i_state &= ~I_OVL_INUSE;
+ spin_unlock(&inode->i_lock);
+ }
+}