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-rw-r--r--Documentation/btrfs-filesystem.asciidoc11
-rw-r--r--Documentation/btrfs-mount.asciidoc7
2 files changed, 14 insertions, 4 deletions
diff --git a/Documentation/btrfs-filesystem.asciidoc b/Documentation/btrfs-filesystem.asciidoc
index 31cd51be..600bbac0 100644
--- a/Documentation/btrfs-filesystem.asciidoc
+++ b/Documentation/btrfs-filesystem.asciidoc
@@ -55,6 +55,13 @@ if the free space is too fragmented.
Use 0 to take the kernel default, which is 256kB but may change in the future.
You can also turn on compression in defragment operations.
+
+WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as well as
+with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or ≥ 3.13.4 will break up
+the ref-links of CoW data (for example files copied with `cp --reflink`,
+snapshots or de-duplicated data).
+This may cause considerable increase of space usage depending on the broken up
+ref-links.
++
`Options`
+
-v::::
@@ -79,10 +86,6 @@ target extent size, do not touch extents bigger than <size>
For <start>, <len>, <size> it is possible to append
units designator: \'K', \'M', \'G', \'T', \'P', or \'E', which represent
KiB, MiB, GiB, TiB, PiB, or EiB, respectively. Case does not matter.
-+
-WARNING: defragmenting with kernels up to 2.6.37 will unlink COW-ed copies of data,
-don't use it if you use snapshots, have de-duplicated your data or made
-copies with `cp --reflink`.
*label* [<dev>|<mountpoint>] [<newlabel>]::
Show or update the label of a filesystem.
diff --git a/Documentation/btrfs-mount.asciidoc b/Documentation/btrfs-mount.asciidoc
index 39215a8e..d364594f 100644
--- a/Documentation/btrfs-mount.asciidoc
+++ b/Documentation/btrfs-mount.asciidoc
@@ -26,6 +26,13 @@ MOUNT OPTIONS
Auto defragmentation detects small random writes into files and queue
them up for the defrag process. Works best for small files;
Not well suited for large database workloads.
+ +
+ WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as
+ well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or
+ ≥ 3.13.4 will break up the ref-links of CoW data (for example files
+ copied with `cp --reflink`, snapshots or de-duplicated data).
+ This may cause considerable increase of space usage depending on the
+ broken up ref-links.
*check_int*::
*check_int_data*::