LU-2244 lov: remove unused bits from lov, osc

[fs/lustre-release.git] / lustre / osp / osp_precreate.c

diff --git a/lustre/osp/osp_precreate.c b/lustre/osp/osp_precreate.c
index 5df08e9..4adf222 100644 (file)
--- a/lustre/osp/osp_precreate.c
+++ b/lustre/osp/osp_precreate.c
@@ -469,6 +469,20 @@ void osp_pre_update_status(struct osp_device *d, int rc)
        if (rc)
                goto out;
 
+       /* Add a bit of hysteresis so this flag isn't continually flapping,
+        * and ensure that new files don't get extremely fragmented due to
+        * only a small amount of available space in the filesystem.
+        * We want to set the NOSPC flag when there is less than ~0.1% free
+        * and clear it when there is at least ~0.2% free space, so:
+        *                   avail < ~0.1% max          max = avail + used
+        *            1025 * avail < avail + used       used = blocks - free
+        *            1024 * avail < used
+        *            1024 * avail < blocks - free
+        *                   avail < ((blocks - free) >> 10)
+        *
+        * On very large disk, say 16TB 0.1% will be 16 GB. We don't want to
+        * lose that amount of space so in those cases we report no space left
+        * if their is less than 1 GB left.                             */
        if (likely(msfs->os_type)) {
                used = min_t(__u64, (msfs->os_blocks - msfs->os_bfree) >> 10,
                                    1 << 30);