xfs: add EOFBLOCKS inode tagging/untagging

Add the XFS_ICI_EOFBLOCKS_TAG inode tag to identify inodes with
speculatively preallocated blocks beyond EOF. An inode is tagged
when speculative preallocation occurs and untagged either via
truncate down or when post-EOF blocks are freed via release or
reclaim.

The tag management is intentionally not aggressive to prefer
simplicity over the complexity of handling all the corner cases
under which post-EOF blocks could be freed (i.e., forward
truncation, fallocate, write error conditions, etc.). This means
that a tagged inode may or may not have post-EOF blocks after a
period of time. The tag is eventually cleared when the inode is
released or reclaimed.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_ag.h

@@ -233,6 +233,7 @@ typedef struct xfs_perag {
 #define XFS_ICI_NO_TAG		(-1)	/* special flag for an untagged lookup
 					   in xfs_inode_ag_iterator */
 #define XFS_ICI_RECLAIM_TAG	0	/* inode is to be reclaimed */
+#define XFS_ICI_EOFBLOCKS_TAG	1	/* inode has blocks beyond EOF */
 
 #define	XFS_AG_MAXLEVELS(mp)		((mp)->m_ag_maxlevels)
 #define	XFS_MIN_FREELIST_RAW(bl,cl,mp)	\

fs/xfs/xfs_icache.c

@@ -1128,3 +1128,65 @@ xfs_reclaim_inodes_count(
 	return reclaimable;
 }
 
+void
+xfs_inode_set_eofblocks_tag(
+	xfs_inode_t	*ip)
+{
+	struct xfs_mount *mp = ip->i_mount;
+	struct xfs_perag *pag;
+	int tagged;
+
+	pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
+	spin_lock(&pag->pag_ici_lock);
+	trace_xfs_inode_set_eofblocks_tag(ip);
+
+	tagged = radix_tree_tagged(&pag->pag_ici_root,
+				   XFS_ICI_EOFBLOCKS_TAG);
+	radix_tree_tag_set(&pag->pag_ici_root,
+			   XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
+			   XFS_ICI_EOFBLOCKS_TAG);
+	if (!tagged) {
+		/* propagate the eofblocks tag up into the perag radix tree */
+		spin_lock(&ip->i_mount->m_perag_lock);
+		radix_tree_tag_set(&ip->i_mount->m_perag_tree,
+				   XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
+				   XFS_ICI_EOFBLOCKS_TAG);
+		spin_unlock(&ip->i_mount->m_perag_lock);
+
+		trace_xfs_perag_set_eofblocks(ip->i_mount, pag->pag_agno,
+					      -1, _RET_IP_);
+	}
+
+	spin_unlock(&pag->pag_ici_lock);
+	xfs_perag_put(pag);
+}
+
+void
+xfs_inode_clear_eofblocks_tag(
+	xfs_inode_t	*ip)
+{
+	struct xfs_mount *mp = ip->i_mount;
+	struct xfs_perag *pag;
+
+	pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
+	spin_lock(&pag->pag_ici_lock);
+	trace_xfs_inode_clear_eofblocks_tag(ip);
+
+	radix_tree_tag_clear(&pag->pag_ici_root,
+			     XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
+			     XFS_ICI_EOFBLOCKS_TAG);
+	if (!radix_tree_tagged(&pag->pag_ici_root, XFS_ICI_EOFBLOCKS_TAG)) {
+		/* clear the eofblocks tag from the perag radix tree */
+		spin_lock(&ip->i_mount->m_perag_lock);
+		radix_tree_tag_clear(&ip->i_mount->m_perag_tree,
+				     XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
+				     XFS_ICI_EOFBLOCKS_TAG);
+		spin_unlock(&ip->i_mount->m_perag_lock);
+		trace_xfs_perag_clear_eofblocks(ip->i_mount, pag->pag_agno,
+					       -1, _RET_IP_);
+	}
+
+	spin_unlock(&pag->pag_ici_lock);
+	xfs_perag_put(pag);
+}
+

fs/xfs/xfs_icache.h

@@ -35,6 +35,9 @@ void xfs_reclaim_inodes_nr(struct xfs_mount *mp, int nr_to_scan);
 
 void xfs_inode_set_reclaim_tag(struct xfs_inode *ip);
 
+void xfs_inode_set_eofblocks_tag(struct xfs_inode *ip);
+void xfs_inode_clear_eofblocks_tag(struct xfs_inode *ip);
+
 int xfs_sync_inode_grab(struct xfs_inode *ip);
 int xfs_inode_ag_iterator(struct xfs_mount *mp,
 	int (*execute)(struct xfs_inode *ip, struct xfs_perag *pag, int flags),

fs/xfs/xfs_iomap.c

@@ -41,6 +41,7 @@
 #include "xfs_utils.h"
 #include "xfs_iomap.h"
 #include "xfs_trace.h"
+#include "xfs_icache.h"
 
 
 #define XFS_WRITEIO_ALIGN(mp,off)	(((off) >> mp->m_writeio_log) \
@@ -450,6 +451,13 @@ retry:
 	if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))
 		return xfs_alert_fsblock_zero(ip, &imap[0]);
 
+	/*
+	 * Tag the inode as speculatively preallocated so we can reclaim this
+	 * space on demand, if necessary.
+	 */
+	if (prealloc)
+		xfs_inode_set_eofblocks_tag(ip);
+
 	*ret_imap = imap[0];
 	return 0;
 }

fs/xfs/xfs_iops.c

@@ -38,6 +38,7 @@
 #include "xfs_vnodeops.h"
 #include "xfs_inode_item.h"
 #include "xfs_trace.h"
+#include "xfs_icache.h"
 
 #include <linux/capability.h>
 #include <linux/xattr.h>
@@ -854,6 +855,9 @@ xfs_setattr_size(
 		 * and do not wait the usual (long) time for writeout.
 		 */
 		xfs_iflags_set(ip, XFS_ITRUNCATED);
+
+		/* A truncate down always removes post-EOF blocks. */
+		xfs_inode_clear_eofblocks_tag(ip);
 	}
 
 	if (mask & ATTR_CTIME) {

fs/xfs/xfs_trace.h

@@ -130,6 +130,8 @@ DEFINE_PERAG_REF_EVENT(xfs_perag_get_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_put);
 DEFINE_PERAG_REF_EVENT(xfs_perag_set_reclaim);
 DEFINE_PERAG_REF_EVENT(xfs_perag_clear_reclaim);
+DEFINE_PERAG_REF_EVENT(xfs_perag_set_eofblocks);
+DEFINE_PERAG_REF_EVENT(xfs_perag_clear_eofblocks);
 
 TRACE_EVENT(xfs_attr_list_node_descend,
 	TP_PROTO(struct xfs_attr_list_context *ctx,
@@ -585,6 +587,9 @@ DEFINE_INODE_EVENT(xfs_update_time);
 DEFINE_INODE_EVENT(xfs_dquot_dqalloc);
 DEFINE_INODE_EVENT(xfs_dquot_dqdetach);
 
+DEFINE_INODE_EVENT(xfs_inode_set_eofblocks_tag);
+DEFINE_INODE_EVENT(xfs_inode_clear_eofblocks_tag);
+
 DECLARE_EVENT_CLASS(xfs_iref_class,
 	TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip),
 	TP_ARGS(ip, caller_ip),

fs/xfs/xfs_vnodeops.c

@@ -238,6 +238,8 @@ xfs_free_eofblocks(
 		} else {
 			error = xfs_trans_commit(tp,
 						XFS_TRANS_RELEASE_LOG_RES);
+			if (!error)
+				xfs_inode_clear_eofblocks_tag(ip);
 		}
 
 		xfs_iunlock(ip, XFS_ILOCK_EXCL);