xfs: commit CoW-based atomic writes atomically

Source kernel commit: b1e09178b73adf10dc87fba9aee7787a7ad26874

When completing a CoW-based write, each extent range mapping update is
covered by a separate transaction.

For a CoW-based atomic write, all mappings must be changed at once, so
change to use a single transaction.

Note that there is a limit on the amount of log intent items which can be
fit into a single transaction, but this is being ignored for now since
the count of items for a typical atomic write would be much less than is
typically supported. A typical atomic write would be expected to be 64KB
or less, which means only 16 possible extents unmaps, which is quite
small.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: add tr_atomic_ioend]
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>

diff --git a/libxfs/xfs_log_rlimit.c b/libxfs/xfs_log_rlimit.c
index 246d5f486d024afcfcba82716d867c7d728b8e24..2b9047f5ffb58bfe362e126307550c0b82aebcdd 100644 (file)
--- a/libxfs/xfs_log_rlimit.c
+++ b/libxfs/xfs_log_rlimit.c
@@ -91,6 +91,7 @@ xfs_log_calc_trans_resv_for_minlogblocks(
         */
        if (xfs_want_minlogsize_fixes(&mp->m_sb)) {
                xfs_trans_resv_calc(mp, resv);
+               resv->tr_atomic_ioend = M_RES(mp)->tr_atomic_ioend;
                return;
        }
 
@@ -107,6 +108,9 @@ xfs_log_calc_trans_resv_for_minlogblocks(
 
        xfs_trans_resv_calc(mp, resv);
 
+       /* Copy the dynamic transaction reservation types from the running fs */
+       resv->tr_atomic_ioend = M_RES(mp)->tr_atomic_ioend;
+
        if (xfs_has_reflink(mp)) {
                /*
                 * In the early days of reflink, typical log operation counts

diff --git a/libxfs/xfs_trans_resv.c b/libxfs/xfs_trans_resv.c
index 0a843deb50a118ac7709ebdf7a83b65861ec6dfe..cf735f946c8ac739203ae9cabaace6ff53082f4a 100644 (file)
--- a/libxfs/xfs_trans_resv.c
+++ b/libxfs/xfs_trans_resv.c
@@ -1281,6 +1281,15 @@ xfs_calc_namespace_reservations(
        resp->tr_mkdir.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 }
 
+STATIC void
+xfs_calc_default_atomic_ioend_reservation(
+       struct xfs_mount        *mp,
+       struct xfs_trans_resv   *resp)
+{
+       /* Pick a default that will scale reasonably for the log size. */
+       resp->tr_atomic_ioend = resp->tr_itruncate;
+}
+
 void
 xfs_trans_resv_calc(
        struct xfs_mount        *mp,
@@ -1375,4 +1384,10 @@ xfs_trans_resv_calc(
        resp->tr_itruncate.tr_logcount += logcount_adj;
        resp->tr_write.tr_logcount += logcount_adj;
        resp->tr_qm_dqalloc.tr_logcount += logcount_adj;
+
+       /*
+        * Now that we've finished computing the static reservations, we can
+        * compute the dynamic reservation for atomic writes.
+        */
+       xfs_calc_default_atomic_ioend_reservation(mp, resp);
 }

diff --git a/libxfs/xfs_trans_resv.h b/libxfs/xfs_trans_resv.h
index d9d0032cbbc5d4a8a3e1ccdfaa289b1304a4112a..670045d417a65fd6ac04a0fb449351d30ba2e648 100644 (file)
--- a/libxfs/xfs_trans_resv.h
+++ b/libxfs/xfs_trans_resv.h
@@ -48,6 +48,7 @@ struct xfs_trans_resv {
        struct xfs_trans_res    tr_qm_dqalloc;  /* allocate quota on disk */
        struct xfs_trans_res    tr_sb;          /* modify superblock */
        struct xfs_trans_res    tr_fsyncts;     /* update timestamps on fsync */
+       struct xfs_trans_res    tr_atomic_ioend; /* untorn write completion */
 };
 
 /* shorthand way of accessing reservation structure */