[PATCH 2/3] xfs: add a free space extent change reservation

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

Lots of the transaction reservation code reserves space for an
extent allocation. It is inconsistently implemented, and many of
them get it wrong. Introduce a new function to calculate the log
space reservation for adding or removing an extent from the free
space btrees.

This function reserves space for logging the AGF, the AGFL and the
free space btrees, avoiding the need to account for them seperately
in every reservation that manipulates free space.

Convert the EFI recovery reservation to use this transaction
reservation as EFI recovery only needs to manipulate the free space
index.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/libxfs/xfs_trans_resv.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index da2ec052ac0a..621ddb277dfa 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -79,6 +79,23 @@ xfs_allocfree_log_count(
 	return blocks;
 }
 
+/*
+ * Log reservation required to add or remove a single extent to the free space
+ * btrees.  This requires modifying:
+ *
+ * the agf header: 1 sector
+ * the agfl header: 1 sector
+ * the allocation btrees: 2 trees * (max depth - 1) * block size
+ */
+uint
+xfs_allocfree_extent_res(
+	struct xfs_mount *mp)
+{
+	return xfs_calc_buf_res(2, mp->m_sb.sb_sectsize) +
+	       xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+				XFS_FSB_TO_B(mp, 1));
+}
+
 /*
  * Logging inodes is really tricksy. They are logged in memory format,
  * which means that what we write into the log doesn't directly translate into
@@ -922,7 +939,7 @@ xfs_trans_resv_calc(
 	 * EFI recovery is itruncate minus the initial transaction that logs
 	 * logs the EFI.
 	 */
-	resp->tr_efi.tr_logres = resp->tr_itruncate.tr_logres;
+	resp->tr_efi.tr_logres = xfs_allocfree_extent_res(mp);
 	resp->tr_efi.tr_logcount = resp->tr_itruncate.tr_logcount - 1;
 	resp->tr_efi.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
-- 
2.28.0