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authorJ. Bruce Fields <bfields@fieldses.org>2011-01-18 15:45:09 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-10 05:18:54 -0500
commitd891eedbc3b1b0fade8a9ce60cc0eba1cccb59e5 (patch)
tree55dd6aa9e17cd763efda6291d740bafd7f05d802 /fs
parent1ca551c6caae7b52178555cdedea6ca26444be46 (diff)
downloadkernel-d891eedbc3b1b0fade8a9ce60cc0eba1cccb59e5.tar.gz
fs/dcache: allow d_obtain_alias() to return unhashed dentries
Without this patch, inodes are not promptly freed on last close of an unlinked file by an nfs client: client$ mount -tnfs4 server:/export/ /mnt/ client$ tail -f /mnt/FOO ... server$ df -i /export server$ rm /export/FOO (^C the tail -f) server$ df -i /export server$ echo 2 >/proc/sys/vm/drop_caches server$ df -i /export the df's will show that the inode is not freed on the filesystem until the last step, when it could have been freed after killing the client's tail -f. On-disk data won't be deallocated either, leading to possible spurious ENOSPC. This occurs because when the client does the close, it arrives in a compound with a putfh and a close, processed like: - putfh: look up the filehandle.  The only alias found for the inode will be DCACHE_UNHASHED alias referenced by the filp this, so it creates a new DCACHE_DISCONECTED dentry and returns that instead. - close: closes the existing filp, which is destroyed immediately by dput() since it's DCACHE_UNHASHED. - end of the compound: release the reference to the current filehandle, and dput() the new DCACHE_DISCONECTED dentry, which gets put on the unused list instead of being destroyed immediately. Nick Piggin suggested fixing this by allowing d_obtain_alias to return the unhashed dentry that is referenced by the filp, instead of making it create a new dentry. Leave __d_find_alias() alone to avoid changing behavior of other callers. Also nfsd doesn't need all the checks of __d_find_alias(); any dentry, hashed or unhashed, disconnected or not, should work. Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c26
1 files changed, 24 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 2a6bd9a4ae97..611ffe928c03 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1523,6 +1523,28 @@ struct dentry * d_alloc_root(struct inode * root_inode)
}
EXPORT_SYMBOL(d_alloc_root);
+static struct dentry * __d_find_any_alias(struct inode *inode)
+{
+ struct dentry *alias;
+
+ if (list_empty(&inode->i_dentry))
+ return NULL;
+ alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
+ __dget(alias);
+ return alias;
+}
+
+static struct dentry * d_find_any_alias(struct inode *inode)
+{
+ struct dentry *de;
+
+ spin_lock(&inode->i_lock);
+ de = __d_find_any_alias(inode);
+ spin_unlock(&inode->i_lock);
+ return de;
+}
+
+
/**
* d_obtain_alias - find or allocate a dentry for a given inode
* @inode: inode to allocate the dentry for
@@ -1552,7 +1574,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
if (IS_ERR(inode))
return ERR_CAST(inode);
- res = d_find_alias(inode);
+ res = d_find_any_alias(inode);
if (res)
goto out_iput;
@@ -1565,7 +1587,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
spin_lock(&inode->i_lock);
- res = __d_find_alias(inode, 0);
+ res = __d_find_any_alias(inode);
if (res) {
spin_unlock(&inode->i_lock);
dput(tmp);