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    Subject[PATCH V10 10/11] fs: Introduce DCACHE_DONTCACHE
    Date
    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 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 | 4 ++++
    fs/inode.c | 15 +++++++++++++++
    fs/xfs/xfs_icache.c | 2 +-
    include/linux/dcache.h | 2 ++
    include/linux/fs.h | 1 +
    5 files changed, 23 insertions(+), 1 deletion(-)

    diff --git a/fs/dcache.c b/fs/dcache.c
    index b280e07e162b..0030fabab2c4 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)))
    diff --git a/fs/inode.c b/fs/inode.c
    index 93d9252a00ab..316355433797 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -1526,6 +1526,21 @@ int generic_delete_inode(struct inode *inode)
    }
    EXPORT_SYMBOL(generic_delete_inode);

    +void mark_inode_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(mark_inode_dontcache);
    +
    /*
    * Called when we're dropping the last reference
    * to an inode.
    diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
    index de76f7f60695..3c8f44477804 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;
    + mark_inode_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..064168ec2e0b 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 mark_inode_dontcache(struct inode *inode);

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