[XFS] Avoid replaying inode buffer initialisation log items if on-disk version is newer.

SGI-PV: 969656
SGI-Modid: xfs-linux-melb:xfs-kern:29676a

Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>

3 files changed, 54 insertions, 3 deletions

diff --git a/fs/xfs/xfs_buf_item.h b/fs/xfs/xfs_buf_item.h
index d7e136143066..fa25b7dcc6c3 100644
--- a/fs/xfs/xfs_buf_item.h
+++ b/fs/xfs/xfs_buf_item.h
@@ -52,6 +52,11 @@ typedef struct xfs_buf_log_format_t {
 #define XFS_BLI_UDQUOT_BUF      0x4
 #define XFS_BLI_PDQUOT_BUF      0x8
 #define XFS_BLI_GDQUOT_BUF      0x10
+/*
+ * This flag indicates that the buffer contains newly allocated
+ * inodes.
+ */
+#define XFS_BLI_INODE_NEW_BUF   0x20
 
 #define XFS_BLI_CHUNK           128
 #define XFS_BLI_SHIFT           7
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 8ae6e8e5f3db..dacb19739cc2 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1874,6 +1874,7 @@ xlog_recover_do_inode_buffer(
 /*ARGSUSED*/
 STATIC void
 xlog_recover_do_reg_buffer(
+        xfs_mount_t             *mp,
         xlog_recover_item_t     *item,
         xfs_buf_t               *bp,
         xfs_buf_log_format_t    *buf_f)
@@ -1884,6 +1885,50 @@ xlog_recover_do_reg_buffer(
         unsigned int            *data_map = NULL;
         unsigned int            map_size = 0;
         int                     error;
+        int                     stale_buf = 1;
+
+        /*
+         * Scan through the on-disk inode buffer and attempt to
+         * determine if it has been written to since it was logged.
+         *
+         * - If any of the magic numbers are incorrect then the buffer is stale
+         * - If any of the modes are non-zero then the buffer is not stale
+         * - If all of the modes are zero and at least one of the generation
+         *   counts is non-zero then the buffer is stale
+         *
+         * If the end result is a stale buffer then the log buffer is replayed
+         * otherwise it is skipped.
+         *
+         * This heuristic is not perfect.  It can be improved by scanning the
+         * entire inode chunk for evidence that any of the inode clusters have
+         * been updated.  To fix this problem completely we will need a major
+         * architectural change to the logging system.
+         */
+        if (buf_f->blf_flags & XFS_BLI_INODE_NEW_BUF) {
+                xfs_dinode_t    *dip;
+                int             inodes_per_buf;
+                int             mode_count = 0;
+                int             gen_count = 0;
+
+                stale_buf = 0;
+                inodes_per_buf = XFS_BUF_COUNT(bp) >> mp->m_sb.sb_inodelog;
+                for (i = 0; i < inodes_per_buf; i++) {
+                        dip = (xfs_dinode_t *)xfs_buf_offset(bp,
+                                i * mp->m_sb.sb_inodesize);
+                        if (be16_to_cpu(dip->di_core.di_magic) !=
+                                        XFS_DINODE_MAGIC) {
+                                stale_buf = 1;
+                                break;
+                        }
+                        if (be16_to_cpu(dip->di_core.di_mode))
+                                mode_count++;
+                        if (be16_to_cpu(dip->di_core.di_gen))
+                                gen_count++;
+                }
+
+                if (!mode_count && gen_count)
+                        stale_buf = 1;
+        }
 
         switch (buf_f->blf_type) {
         case XFS_LI_BUF:
@@ -1917,7 +1962,7 @@ xlog_recover_do_reg_buffer(
                                                -1, 0, XFS_QMOPT_DOWARN,
                                                "dquot_buf_recover");
                 }
-                if (!error)
+                if (!error && stale_buf)
                         memcpy(xfs_buf_offset(bp,
                                 (uint)bit << XFS_BLI_SHIFT),    /* dest */
                                 item->ri_buf[i].i_addr,         /* source */
@@ -2089,7 +2134,7 @@ xlog_recover_do_dquot_buffer(
         if (log->l_quotaoffs_flag & type)
                 return;
 
-        xlog_recover_do_reg_buffer(item, bp, buf_f);
+        xlog_recover_do_reg_buffer(mp, item, bp, buf_f);
 }
 
 /*
@@ -2190,7 +2235,7 @@ xlog_recover_do_buffer_trans(
                   (XFS_BLI_UDQUOT_BUF|XFS_BLI_PDQUOT_BUF|XFS_BLI_GDQUOT_BUF)) {
                 xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
         } else {
-                xlog_recover_do_reg_buffer(item, bp, buf_f);
+                xlog_recover_do_reg_buffer(mp, item, bp, buf_f);
         }
         if (error)
                 return XFS_ERROR(error);
diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index 60b6b898022b..95fff6872a2f 100644
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -966,6 +966,7 @@ xfs_trans_inode_alloc_buf(
         ASSERT(atomic_read(&bip->bli_refcount) > 0);
 
         bip->bli_flags |= XFS_BLI_INODE_ALLOC_BUF;
+        bip->bli_format.blf_flags |= XFS_BLI_INODE_NEW_BUF;
 }