1 files changed, 136 insertions, 0 deletions

diff --git a/fs/xfs/xfs_filestream.h b/fs/xfs/xfs_filestream.h
new file mode 100644
index 000000000000..f655f7dc334c
--- /dev/null
+++ b/fs/xfs/xfs_filestream.h
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2006-2007 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#ifndef __XFS_FILESTREAM_H__
+#define __XFS_FILESTREAM_H__
+
+#ifdef __KERNEL__
+
+struct xfs_mount;
+struct xfs_inode;
+struct xfs_perag;
+struct xfs_bmalloca;
+
+#ifdef XFS_FILESTREAMS_TRACE
+#define XFS_FSTRM_KTRACE_INFO           1
+#define XFS_FSTRM_KTRACE_AGSCAN         2
+#define XFS_FSTRM_KTRACE_AGPICK1        3
+#define XFS_FSTRM_KTRACE_AGPICK2        4
+#define XFS_FSTRM_KTRACE_UPDATE         5
+#define XFS_FSTRM_KTRACE_FREE           6
+#define XFS_FSTRM_KTRACE_ITEM_LOOKUP    7
+#define XFS_FSTRM_KTRACE_ASSOCIATE      8
+#define XFS_FSTRM_KTRACE_MOVEAG         9
+#define XFS_FSTRM_KTRACE_ORPHAN         10
+
+#define XFS_FSTRM_KTRACE_SIZE   16384
+extern ktrace_t *xfs_filestreams_trace_buf;
+
+#endif
+
+/*
+ * Allocation group filestream associations are tracked with per-ag atomic
+ * counters.  These counters allow _xfs_filestream_pick_ag() to tell whether a
+ * particular AG already has active filestreams associated with it. The mount
+ * point's m_peraglock is used to protect these counters from per-ag array
+ * re-allocation during a growfs operation.  When xfs_growfs_data_private() is
+ * about to reallocate the array, it calls xfs_filestream_flush() with the
+ * m_peraglock held in write mode.
+ *
+ * Since xfs_mru_cache_flush() guarantees that all the free functions for all
+ * the cache elements have finished executing before it returns, it's safe for
+ * the free functions to use the atomic counters without m_peraglock protection.
+ * This allows the implementation of xfs_fstrm_free_func() to be agnostic about
+ * whether it was called with the m_peraglock held in read mode, write mode or
+ * not held at all.  The race condition this addresses is the following:
+ *
+ *  - The work queue scheduler fires and pulls a filestream directory cache
+ *    element off the LRU end of the cache for deletion, then gets pre-empted.
+ *  - A growfs operation grabs the m_peraglock in write mode, flushes all the
+ *    remaining items from the cache and reallocates the mount point's per-ag
+ *    array, resetting all the counters to zero.
+ *  - The work queue thread resumes and calls the free function for the element
+ *    it started cleaning up earlier.  In the process it decrements the
+ *    filestreams counter for an AG that now has no references.
+ *
+ * With a shrinkfs feature, the above scenario could panic the system.
+ *
+ * All other uses of the following macros should be protected by either the
+ * m_peraglock held in read mode, or the cache's internal locking exposed by the
+ * interval between a call to xfs_mru_cache_lookup() and a call to
+ * xfs_mru_cache_done().  In addition, the m_peraglock must be held in read mode
+ * when new elements are added to the cache.
+ *
+ * Combined, these locking rules ensure that no associations will ever exist in
+ * the cache that reference per-ag array elements that have since been
+ * reallocated.
+ */
+STATIC_INLINE int
+xfs_filestream_peek_ag(
+        xfs_mount_t     *mp,
+        xfs_agnumber_t  agno)
+{
+        return atomic_read(&mp->m_perag[agno].pagf_fstrms);
+}
+
+STATIC_INLINE int
+xfs_filestream_get_ag(
+        xfs_mount_t     *mp,
+        xfs_agnumber_t  agno)
+{
+        return atomic_inc_return(&mp->m_perag[agno].pagf_fstrms);
+}
+
+STATIC_INLINE int
+xfs_filestream_put_ag(
+        xfs_mount_t     *mp,
+        xfs_agnumber_t  agno)
+{
+        return atomic_dec_return(&mp->m_perag[agno].pagf_fstrms);
+}
+
+/* allocation selection flags */
+typedef enum xfs_fstrm_alloc {
+        XFS_PICK_USERDATA = 1,
+        XFS_PICK_LOWSPACE = 2,
+} xfs_fstrm_alloc_t;
+
+/* prototypes for filestream.c */
+int xfs_filestream_init(void);
+void xfs_filestream_uninit(void);
+int xfs_filestream_mount(struct xfs_mount *mp);
+void xfs_filestream_unmount(struct xfs_mount *mp);
+void xfs_filestream_flush(struct xfs_mount *mp);
+xfs_agnumber_t xfs_filestream_lookup_ag(struct xfs_inode *ip);
+int xfs_filestream_associate(struct xfs_inode *dip, struct xfs_inode *ip);
+void xfs_filestream_deassociate(struct xfs_inode *ip);
+int xfs_filestream_new_ag(struct xfs_bmalloca *ap, xfs_agnumber_t *agp);
+
+
+/* filestreams for the inode? */
+STATIC_INLINE int
+xfs_inode_is_filestream(
+        struct xfs_inode        *ip)
+{
+        return (ip->i_mount->m_flags & XFS_MOUNT_FILESTREAMS) ||
+                xfs_iflags_test(ip, XFS_IFILESTREAM) ||
+                (ip->i_d.di_flags & XFS_DIFLAG_FILESTREAM);
+}
+
+#endif /* __KERNEL__ */
+
+#endif /* __XFS_FILESTREAM_H__ */