Commit 590fb51f authored Aug 13, 2013 by Yan, Zheng Committed by Al Viro Sep 03, 2013

vfs: call d_op->d_prune() before unhashing dentry



The d_prune dentry operation is used to notify filesystem when VFS
about to prune a hashed dentry from the dcache. There are three
code paths that prune dentries: shrink_dcache_for_umount_subtree(),
prune_dcache_sb() and d_prune_aliases(). For the d_prune_aliases()
case, VFS unhashes the dentry first, then call the d_prune dentry
operation. This confuses ceph_d_prune() (ceph uses the d_prune
dentry operation to maintain a flag indicating whether the complete
contents of a directory are in the dcache, pruning unhashed dentry
does not affect dir's completeness)

This patch fixes the issue by calling the d_prune dentry operation
in d_prune_aliases(), before unhashing the dentry. Also make VFS
only call the d_prune dentry operation for hashed dentry, to avoid
calling the d_prune dentry operation twice when dentry is pruned
by d_prune_aliases().

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 184cacab

fs/dcache.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -472,7 +472,7 @@ relock:
		* inform the fs via d_prune that this dentry is about to be
		* unhashed and destroyed.
		*/
		if (dentry->d_flags & DCACHE_OP_PRUNE)
		if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
		dentry->d_op->d_prune(dentry);

		dentry_lru_del(dentry);
		@@ -719,6 +719,14 @@ restart:
		hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
		spin_lock(&dentry->d_lock);
		if (!dentry->d_count) {
		/*
		* inform the fs via d_prune that this dentry
		* is about to be unhashed and destroyed.
		*/
		if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
		!d_unhashed(dentry))
		dentry->d_op->d_prune(dentry);

		__dget_dlock(dentry);
		__d_drop(dentry);
		spin_unlock(&dentry->d_lock);
		@@ -907,7 +915,8 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
		* inform the fs that this dentry is about to be
		* unhashed and destroyed.
		*/
		if (dentry->d_flags & DCACHE_OP_PRUNE)
		if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
		!d_unhashed(dentry))
		dentry->d_op->d_prune(dentry);

		dentry_lru_del(dentry);

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