[PATCH 2/2] xfs: move the check for post-EOF mappings into xfs_can_free_eofblocks

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Fix the weird split of responsibilities between xfs_can_free_eofblocks
and xfs_free_eofblocks by moving the chunk of code that looks for any
actual post-EOF space mappings from the second function into the first.

This clears the way for deferred inode inactivation to be able to decide
if an inode needs inactivation work before committing the released inode
to the inactivation code paths (vs. marking it for reclaim).

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_bmap_util.c |  148 +++++++++++++++++++++++++-----------------------
 1 file changed, 78 insertions(+), 70 deletions(-)


diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index e7d68318e6a5..d4ceba5370c7 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -597,8 +597,17 @@ xfs_bmap_punch_delalloc_range(
  * regular files that are marked preallocated or append-only.
  */
 bool
-xfs_can_free_eofblocks(struct xfs_inode *ip, bool force)
+xfs_can_free_eofblocks(
+	struct xfs_inode	*ip,
+	bool			force)
 {
+	struct xfs_bmbt_irec	imap;
+	struct xfs_mount	*mp = ip->i_mount;
+	xfs_fileoff_t		end_fsb;
+	xfs_fileoff_t		last_fsb;
+	int			nimaps = 1;
+	int			error;
+
 	/* prealloc/delalloc exists only on regular files */
 	if (!S_ISREG(VFS_I(ip)->i_mode))
 		return false;
@@ -624,91 +633,90 @@ xfs_can_free_eofblocks(struct xfs_inode *ip, bool force)
 		if (!force || ip->i_delayed_blks == 0)
 			return false;
 
-	return true;
-}
-
-/*
- * This is called to free any blocks beyond eof. The caller must hold
- * IOLOCK_EXCL unless we are in the inode reclaim path and have the only
- * reference to the inode.
- */
-int
-xfs_free_eofblocks(
-	struct xfs_inode	*ip)
-{
-	struct xfs_trans	*tp;
-	int			error;
-	xfs_fileoff_t		end_fsb;
-	xfs_fileoff_t		last_fsb;
-	xfs_filblks_t		map_len;
-	int			nimaps;
-	struct xfs_bmbt_irec	imap;
-	struct xfs_mount	*mp = ip->i_mount;
-
 	/*
-	 * Figure out if there are any blocks beyond the end
-	 * of the file.  If not, then there is nothing to do.
+	 * Do not try to free post-EOF blocks if EOF is beyond the end of the
+	 * range supported by the page cache, because the truncation will loop
+	 * forever.
 	 */
 	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
 	last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
 	if (last_fsb <= end_fsb)
-		return 0;
-	map_len = last_fsb - end_fsb;
+		return false;
 
-	nimaps = 1;
+	/*
+	 * Look up the mapping for the first block past EOF.  If we can't find
+	 * it, there's nothing to free.
+	 */
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
-	error = xfs_bmapi_read(ip, end_fsb, map_len, &imap, &nimaps, 0);
+	error = xfs_bmapi_read(ip, end_fsb, last_fsb - end_fsb, &imap, &nimaps,
+			0);
 	xfs_iunlock(ip, XFS_ILOCK_SHARED);
+	if (error || nimaps == 0)
+		return false;
 
 	/*
-	 * If there are blocks after the end of file, truncate the file to its
-	 * current size to free them up.
+	 * If there's a real mapping there or there are delayed allocation
+	 * reservations, then we have post-EOF blocks to try to free.
 	 */
-	if (!error && (nimaps != 0) &&
-	    (imap.br_startblock != HOLESTARTBLOCK ||
-	     ip->i_delayed_blks)) {
-		/*
-		 * Attach the dquots to the inode up front.
-		 */
-		error = xfs_qm_dqattach(ip);
-		if (error)
-			return error;
+	return imap.br_startblock != HOLESTARTBLOCK || ip->i_delayed_blks;
+}
 
-		/* wait on dio to ensure i_size has settled */
-		inode_dio_wait(VFS_I(ip));
+/*
+ * This is called to free any blocks beyond eof. The caller must hold
+ * IOLOCK_EXCL unless we are in the inode reclaim path and have the only
+ * reference to the inode.
+ */
+int
+xfs_free_eofblocks(
+	struct xfs_inode	*ip)
+{
+	struct xfs_trans	*tp;
+	struct xfs_mount	*mp = ip->i_mount;
+	int			error;
 
-		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0,
-				&tp);
-		if (error) {
-			ASSERT(XFS_FORCED_SHUTDOWN(mp));
-			return error;
-		}
+	/* Attach the dquots to the inode up front. */
+	error = xfs_qm_dqattach(ip);
+	if (error)
+		return error;
 
-		xfs_ilock(ip, XFS_ILOCK_EXCL);
-		xfs_trans_ijoin(tp, ip, 0);
+	/* Wait on dio to ensure i_size has settled. */
+	inode_dio_wait(VFS_I(ip));
 
-		/*
-		 * Do not update the on-disk file size.  If we update the
-		 * on-disk file size and then the system crashes before the
-		 * contents of the file are flushed to disk then the files
-		 * may be full of holes (ie NULL files bug).
-		 */
-		error = xfs_itruncate_extents_flags(&tp, ip, XFS_DATA_FORK,
-					XFS_ISIZE(ip), XFS_BMAPI_NODISCARD);
-		if (error) {
-			/*
-			 * If we get an error at this point we simply don't
-			 * bother truncating the file.
-			 */
-			xfs_trans_cancel(tp);
-		} else {
-			error = xfs_trans_commit(tp);
-			if (!error)
-				xfs_inode_clear_eofblocks_tag(ip);
-		}
-
-		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
+	if (error) {
+		ASSERT(XFS_FORCED_SHUTDOWN(mp));
+		return error;
 	}
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	xfs_trans_ijoin(tp, ip, 0);
+
+	/*
+	 * Do not update the on-disk file size.  If we update the on-disk file
+	 * size and then the system crashes before the contents of the file are
+	 * flushed to disk then the files may be full of holes (ie NULL files
+	 * bug).
+	 */
+	error = xfs_itruncate_extents_flags(&tp, ip, XFS_DATA_FORK,
+				XFS_ISIZE(ip), XFS_BMAPI_NODISCARD);
+	if (error)
+		goto err_cancel;
+
+	error = xfs_trans_commit(tp);
+	if (error)
+		goto out_unlock;
+
+	xfs_inode_clear_eofblocks_tag(ip);
+	goto out_unlock;
+
+err_cancel:
+	/*
+	 * If we get an error at this point we simply don't
+	 * bother truncating the file.
+	 */
+	xfs_trans_cancel(tp);
+out_unlock:
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;
 }