2 files changed, 17 insertions, 9 deletions

diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 2c4004475e71..84e0deb95abd 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -24,7 +24,8 @@ struct xfs_log_vec {
         struct xfs_log_iovec    *lv_iovecp;     /* iovec array */
         struct xfs_log_item     *lv_item;       /* owner */
         char                    *lv_buf;        /* formatted buffer */
-        int                     lv_buf_len;     /* size of formatted buffer */
+        int                     lv_bytes;       /* accounted space in buffer */
+        int                     lv_buf_len;     /* aligned size of buffer */
         int                     lv_size;        /* size of allocated lv */
 };
 
@@ -52,15 +53,21 @@ xlog_prepare_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec **vecp,
         return vec->i_addr;
 }
 
+/*
+ * We need to make sure the next buffer is naturally aligned for the biggest
+ * basic data type we put into it.  We already accounted for this padding when
+ * sizing the buffer.
+ *
+ * However, this padding does not get written into the log, and hence we have to
+ * track the space used by the log vectors separately to prevent log space hangs
+ * due to inaccurate accounting (i.e. a leak) of the used log space through the
+ * CIL context ticket.
+ */
 static inline void
 xlog_finish_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec *vec, int len)
 {
-        /*
-         * We need to make sure the next buffer is naturally aligned for the
-         * biggest basic data type we put into it.  We already accounted for
-         * this when sizing the buffer.
-         */
         lv->lv_buf_len += round_up(len, sizeof(uint64_t));
+        lv->lv_bytes += len;
         vec->i_len = len;
 }
 
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 7e5455391176..de835da6764d 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -97,7 +97,7 @@ xfs_cil_prepare_item(
 {
         /* Account for the new LV being passed in */
         if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
-                *diff_len += lv->lv_buf_len;
+                *diff_len += lv->lv_bytes;
                 *diff_iovecs += lv->lv_niovecs;
         }
 
@@ -111,7 +111,7 @@ xfs_cil_prepare_item(
         else if (old_lv != lv) {
                 ASSERT(lv->lv_buf_len != XFS_LOG_VEC_ORDERED);
 
-                *diff_len -= old_lv->lv_buf_len;
+                *diff_len -= old_lv->lv_bytes;
                 *diff_iovecs -= old_lv->lv_niovecs;
                 kmem_free(old_lv);
         }
@@ -239,7 +239,7 @@ xlog_cil_insert_format_items(
                          * that the space reservation accounting is correct.
                          */
                         *diff_iovecs -= lv->lv_niovecs;
-                        *diff_len -= lv->lv_buf_len;
+                        *diff_len -= lv->lv_bytes;
                 } else {
                         /* allocate new data chunk */
                         lv = kmem_zalloc(buf_size, KM_SLEEP|KM_NOFS);
@@ -259,6 +259,7 @@ xlog_cil_insert_format_items(
 
                 /* The allocated data region lies beyond the iovec region */
                 lv->lv_buf_len = 0;
+                lv->lv_bytes = 0;
                 lv->lv_buf = (char *)lv + buf_size - nbytes;
                 ASSERT(IS_ALIGNED((unsigned long)lv->lv_buf, sizeof(uint64_t)));