1 files changed, 42 insertions, 13 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 8556c59628ba..81323d73a4ee 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -664,7 +664,10 @@ xfs_log_item_init(
 /*
  * Write region vectors to log.  The write happens using the space reservation
  * of the ticket (tic).  It is not a requirement that all writes for a given
- * transaction occur with one call to xfs_log_write().
+ * transaction occur with one call to xfs_log_write(). However, it is important
+ * to note that the transaction reservation code makes an assumption about the
+ * number of log headers a transaction requires that may be violated if you
+ * don't pass all the transaction vectors in one call....
  */
 int
 xfs_log_write(
@@ -3170,14 +3173,16 @@ xfs_log_ticket_get(
  * Allocate and initialise a new log ticket.
  */
 STATIC xlog_ticket_t *
-xlog_ticket_alloc(xlog_t                *log,
-                int             unit_bytes,
-                int             cnt,
-                char            client,
-                uint            xflags)
+xlog_ticket_alloc(
+        struct log      *log,
+        int             unit_bytes,
+        int             cnt,
+        char            client,
+        uint            xflags)
 {
-        xlog_ticket_t   *tic;
+        struct xlog_ticket *tic;
         uint            num_headers;
+        int             iclog_space;
 
         tic = kmem_zone_zalloc(xfs_log_ticket_zone, KM_SLEEP|KM_MAYFAIL);
         if (!tic)
@@ -3221,16 +3226,40 @@ xlog_ticket_alloc(xlog_t		*log,
         /* for start-rec */
         unit_bytes += sizeof(xlog_op_header_t);
 
-        /* for LR headers */
-        num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log);
+        /*
+         * for LR headers - the space for data in an iclog is the size minus
+         * the space used for the headers. If we use the iclog size, then we
+         * undercalculate the number of headers required.
+         *
+         * Furthermore - the addition of op headers for split-recs might
+         * increase the space required enough to require more log and op
+         * headers, so take that into account too.
+         *
+         * IMPORTANT: This reservation makes the assumption that if this
+         * transaction is the first in an iclog and hence has the LR headers
+         * accounted to it, then the remaining space in the iclog is
+         * exclusively for this transaction.  i.e. if the transaction is larger
+         * than the iclog, it will be the only thing in that iclog.
+         * Fundamentally, this means we must pass the entire log vector to
+         * xlog_write to guarantee this.
+         */
+        iclog_space = log->l_iclog_size - log->l_iclog_hsize;
+        num_headers = howmany(unit_bytes, iclog_space);
+
+        /* for split-recs - ophdrs added when data split over LRs */
+        unit_bytes += sizeof(xlog_op_header_t) * num_headers;
+
+        /* add extra header reservations if we overrun */
+        while (!num_headers ||
+               howmany(unit_bytes, iclog_space) > num_headers) {
+                unit_bytes += sizeof(xlog_op_header_t);
+                num_headers++;
+        }
         unit_bytes += log->l_iclog_hsize * num_headers;
 
         /* for commit-rec LR header - note: padding will subsume the ophdr */
         unit_bytes += log->l_iclog_hsize;
 
-        /* for split-recs - ophdrs added when data split over LRs */
-        unit_bytes += sizeof(xlog_op_header_t) * num_headers;
-
         /* for roundoff padding for transaction data and one for commit record */
         if (xfs_sb_version_haslogv2(&log->l_mp->m_sb) &&
             log->l_mp->m_sb.sb_logsunit > 1) {
@@ -3252,7 +3281,7 @@ xlog_ticket_alloc(xlog_t		*log,
         tic->t_trans_type       = 0;
         if (xflags & XFS_LOG_PERM_RESERV)
                 tic->t_flags |= XLOG_TIC_PERM_RESERV;
-        sv_init(&(tic->t_wait), SV_DEFAULT, "logtick");
+        sv_init(&tic->t_wait, SV_DEFAULT, "logtick");
 
         xlog_tic_reset_res(tic);