Diffstat (limited to 'Documentation/btrfs-filesystem.asciidoc')
1 files changed, 16 insertions, 7 deletions
diff --git a/Documentation/btrfs-filesystem.asciidoc b/Documentation/btrfs-filesystem.asciidoc
index dc032faa..9782af9b 100644
@@ -11,9 +11,10 @@ SYNOPSIS
-*btrfs filesystem* is used to do the whole filesystem level tasks, including
-all the regular filesystem operations like resizing, space stats, label
-setting/getting, and defragmentation.
+*btrfs filesystem* is used to perform several whole filesystem level tasks,
+including all the regular filesystem operations like resizing, space stats,
+label setting/getting, and defragmentation. There are other whole filesystem
+taks like scrub or balance that are grouped in separate commands.
@@ -116,15 +117,23 @@ compression. See also section 'EXAMPLES'.
defragment files recursively in given directories
-flush data for each file before going to the next file. This will limit the amount
-of dirty data to current file, otherwise the amount cumulates from several files
-and may increase system load.
+flush data for each file before going to the next file.
+This will limit the amount of dirty data to current file, otherwise the amount
+cumulates from several files and will increase system load. This can also lead
+to ENOSPC if there's too much dirty data to write and it's not possible to make
+the reservations for the new data (ie. how the COW design works).
defragmentation will start from the given offset, default is beginning of a file
defragment only up to 'len' bytes, default is the file size
-target extent size, do not touch extents bigger than 'size'
+target extent size, do not touch extents bigger than 'size', default: 32M
+The value is only advisory and the final size of the extents may differ,
+depending on the state of the free space and fragmentation or other internal
+logic. Reasonable values are from tens to hundreds of megabytes.
*du* [options] <path> [<path>..]::
Calculate disk usage of the target files using FIEMAP. For individual