xfs: avoid CIL allocation during insert

[~andy/linux] / fs / xfs / xfs_log_cil.c

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 423ceaf0aeb03e2508e1a52aa5819051678a88b6..b20b15761e9c3426bc8d224a38cec1f7d4464c74 100644 (file)
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -185,6 +185,22 @@ xlog_cil_prepare_log_vecs(
                buf_size = sizeof(struct xfs_log_vec) + nbytes +
                                niovecs * sizeof(struct xfs_log_iovec);
 
+               /* compare to existing item size */
+               if (lip->li_lv && buf_size <= lip->li_lv->lv_size) {
+                       /* same or smaller, optimise common overwrite case */
+                       lv = lip->li_lv;
+                       lv->lv_next = NULL;
+
+                       if (ordered)
+                               goto insert;
+
+                       /* Ensure the lv is set up according to ->iop_size */
+                       lv->lv_niovecs = niovecs;
+                       lv->lv_buf = (char *)lv + buf_size - nbytes;
+                       lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv);
+                       goto insert;
+               }
+
                /* allocate new data chunk */
                lv = kmem_zalloc(buf_size, KM_SLEEP|KM_NOFS);
                lv->lv_item = lip;
@@ -204,8 +220,8 @@ xlog_cil_prepare_log_vecs(
                lv->lv_buf = (char *)lv + buf_size - nbytes;
 
                lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv);
-               ASSERT(lv->lv_buf_len <= nbytes);
 insert:
+               ASSERT(lv->lv_buf_len <= nbytes);
                if (!ret_lv)
                        ret_lv = lv;
                else
@@ -230,7 +246,17 @@ xfs_cil_prepare_item(
 {
        struct xfs_log_vec      *old = lv->lv_item->li_lv;
 
-       if (old) {
+       if (!old) {
+               /* new lv, must pin the log item */
+               ASSERT(!lv->lv_item->li_lv);
+
+               if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
+                       *len += lv->lv_buf_len;
+                       *diff_iovecs += lv->lv_niovecs;
+               }
+               lv->lv_item->li_ops->iop_pin(lv->lv_item);
+
+       } else if (old != lv) {
                /* existing lv on log item, space used is a delta */
                ASSERT((old->lv_buf && old->lv_buf_len && old->lv_niovecs) ||
                        old->lv_buf_len == XFS_LOG_VEC_ORDERED);
@@ -249,15 +275,8 @@ xfs_cil_prepare_item(
                *diff_iovecs += lv->lv_niovecs - old->lv_niovecs;
                kmem_free(old);
        } else {
-               /* new lv, must pin the log item */
-               ASSERT(!lv->lv_item->li_lv);
-
-               if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
-                       *len += lv->lv_buf_len;
-                       *diff_iovecs += lv->lv_niovecs;
-               }
-               IOP_PIN(lv->lv_item);
-
+               /* re-used lv */
+               /* XXX: can't account for len/diff_iovecs yet */
        }
 
        /* attach new log vector to log item */
@@ -733,18 +752,13 @@ xfs_log_commit_cil(
        if (flags & XFS_TRANS_RELEASE_LOG_RES)
                log_flags = XFS_LOG_REL_PERM_RESERV;
 
-       /*
-        * Do all the hard work of formatting items (including memory
-        * allocation) outside the CIL context lock. This prevents stalling CIL
-        * pushes when we are low on memory and a transaction commit spends a
-        * lot of time in memory reclaim.
-        */
+       /* lock out background commit */
+       down_read(&log->l_cilp->xc_ctx_lock);
+
        log_vector = xlog_cil_prepare_log_vecs(tp);
        if (!log_vector)
                return ENOMEM;
 
-       /* lock out background commit */
-       down_read(&log->l_cilp->xc_ctx_lock);
        if (commit_lsn)
                *commit_lsn = log->l_cilp->xc_ctx->sequence;