[PATCH V11 10/11] fs: Introduce DCACHE_DONTCACHE

ira.weiny
2020-04-28T00:22:16Z

From: Ira Weiny <ira.weiny@intel.com>

DCACHE_DONTCACHE indicates a dentry should not be cached on final
dput().

Also add a helper function to mark DCACHE_DONTCACHE on all dentries
pointing to a specific inode when that inode is being set I_DONTCACHE.

This facilitates dropping dentry references to inodes sooner which
require eviction to swap S_DAX mode.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from V10:
rename to d_mark_dontcache()
Move function to fs/dcache.c

Changes from V9:
modify i_state under i_lock
Update comment
"Purge from memory on final dput()"

Changes from V8:
Update commit message
Use mark_inode_dontcache in XFS
Fix locking... can't use rcu here.
Change name to mark_inode_dontcache
---
fs/dcache.c | 19 +++++++++++++++++++
fs/xfs/xfs_icache.c | 2 +-
include/linux/dcache.h | 2 ++
include/linux/fs.h | 1 +
4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b280e07e162b..0d07fb335b78 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -647,6 +647,10 @@ static inline bool retain_dentry(struct dentry *dentry)
if (dentry->d_op->d_delete(dentry))
return false;
}
+
+ if (unlikely(dentry->d_flags & DCACHE_DONTCACHE))
+ return false;
+
/* retain; LRU fodder */
dentry->d_lockref.count--;
if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
@@ -656,6 +660,21 @@ static inline bool retain_dentry(struct dentry *dentry)
return true;
}

+void d_mark_dontcache(struct inode *inode)
+{
+ struct dentry *de;
+
+ spin_lock(&inode->i_lock);
+ hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
+ spin_lock(&de->d_lock);
+ de->d_flags |= DCACHE_DONTCACHE;
+ spin_unlock(&de->d_lock);
+ }
+ inode->i_state |= I_DONTCACHE;
+ spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL(d_mark_dontcache);
+
/*
* Finish off a dentry we've decided to kill.
* dentry->d_lock must be held, returns with it unlocked.
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index de76f7f60695..888646d74d7d 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -559,7 +559,7 @@ xfs_iget_cache_miss(
*/
iflags = XFS_INEW;
if (flags & XFS_IGET_DONTCACHE)
- VFS_I(ip)->i_state |= I_DONTCACHE;
+ d_mark_dontcache(VFS_I(ip));
ip->i_udquot = NULL;
ip->i_gdquot = NULL;
ip->i_pdquot = NULL;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c1488cc84fd9..a81f0c3cf352 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -177,6 +177,8 @@ struct dentry_operations {

#define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */

+#define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */
+
#define DCACHE_CANT_MOUNT 0x00000100
#define DCACHE_GENOCIDE 0x00000200
#define DCACHE_SHRINK_LIST 0x00000400
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 44bd45af760f..7c3e8c0306e0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3055,6 +3055,7 @@ static inline int generic_drop_inode(struct inode *inode)
return !inode->i_nlink || inode_unhashed(inode) ||
(inode->i_state & I_DONTCACHE);
}
+extern void d_mark_dontcache(struct inode *inode);

extern struct inode *ilookup5_nowait(struct super_block *sb,
unsigned long hashval, int (*test)(struct inode *, void *),
--
2.25.1