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-rw-r--r--Documentation/mkfs.btrfs.asciidoc35
1 files changed, 34 insertions, 1 deletions
diff --git a/Documentation/mkfs.btrfs.asciidoc b/Documentation/mkfs.btrfs.asciidoc
index a9aa3cb4..5789762a 100644
--- a/Documentation/mkfs.btrfs.asciidoc
+++ b/Documentation/mkfs.btrfs.asciidoc
@@ -133,9 +133,42 @@ UNIT
As default the unit is the byte, however it is possible to append a suffix
to the arguments like 'k' for KBytes, 'm' for MBytes...
+NOTES
+-----
+Since mixed block group creation is optional, we allow small
+filesystem instances with differing values for sectorsize and nodesize
+to be created and could end up in the following situation,
+
+ [root@localhost ~]# mkfs.btrfs -f -n 65536 /dev/loop0
+ btrfs-progs v3.19-rc2-405-g976307c
+ See http://btrfs.wiki.kernel.org for more information.
+
+ Performing full device TRIM (512.00MiB) ...
+ Label: (null)
+ UUID: 49fab72e-0c8b-466b-a3ca-d1bfe56475f0
+ Node size: 65536
+ Sector size: 4096
+ Filesystem size: 512.00MiB
+ Block group profiles:
+ Data: single 8.00MiB
+ Metadata: DUP 40.00MiB
+ System: DUP 12.00MiB
+ SSD detected: no
+ Incompat features: extref, skinny-metadata
+ Number of devices: 1
+ Devices:
+ ID SIZE PATH
+ 1 512.00MiB /dev/loop0
+ [root@localhost ~]# mount /dev/loop0 /mnt/
+ mount: mount /dev/loop0 on /mnt failed: No space left on device
+
+The ENOSPC occurs during the creation of the UUID tree. This is
+because of things like large metadata block size, DUP mode used for
+metadata and global reservation consuming space.
+
AVAILABILITY
------------
-*btrfs* is part of btrfs-progs.
+*mkfs.btrfs* is part of btrfs-progs.
Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
further details.