@@ -9,17 +9,18 @@ to the exactly same size of the block and page. On x86_64 this is typically
pages, like 64KiB on 64bit ARM or PowerPC. This means filesystems created
with 64KiB sector size cannot be mounted on a system with 4KiB page size.
-While with subpage support, systems with 64KiB page size can create (still needs
-"-s 4k" option for mkfs.btrfs) and mount filesystems with 4KiB sectorsize,
-allowing us to push 4KiB sectorsize as default sectorsize for all platforms in the
-near future.
+Since v6.3, filesystems are created with a 4KiB sectorsize by default,
+though it remains possible to create filesystems with other page sizes
+(such as 64KiB with the "-s 64k" option for mkfs.btrfs). This ensures that
+new filesystems are compatible across other architecture variants using
+larger page sizes.
Requirements, limitations
-------------------------
-The initial subpage support has been added in v5.15, although it's still
-considered as experimental at the time of writing (v5.18), most features are
-already working without problems.
+The initial subpage support has been added in v5.15. Most features are
+already working without problems. Subpage support is used by default
+for systems with a non-4KiB page size since v6.3.
End users can mount filesystems with 4KiB sectorsize and do their usual
workload, while should not notice any obvious change, as long as the initial
@@ -116,10 +116,15 @@ OPTIONS
-s|--sectorsize <size>
Specify the sectorsize, the minimum data block allocation unit.
- The default value is the page size and is autodetected. If the sectorsize
- differs from the page size, the created filesystem may not be mountable by the
- running kernel. Therefore it is not recommended to use this option unless you
- are going to mount it on a system with the appropriate page size.
+ By default, the value is 4KiB, but it can be manually set to match the
+ system page size. However, if the sector size is different from the page
+ size, the resulting filesystem may not be mountable by the current
+ kernel, apart from the default 4KiB. Hence, using this option is not
+ advised unless you intend to mount it on a system with the suitable
+ page size.
+
+ .. note::
+ Versions prior to 6.3 set the sectorsize matching to the page size.
-L|--label <string>
Specify a label for the filesystem. The *string* should be less than 256
@@ -1207,7 +1207,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
}
if (!sectorsize)
- sectorsize = (u32)sysconf(_SC_PAGESIZE);
+ sectorsize = (u32)SZ_4K;
if (btrfs_check_sectorsize(sectorsize))
goto error;
We have had working subpage support in Btrfs for many cycles now. Generally, we do not want people creating filesystems by default with non-4k sectorsizes since it creates portability problems. Signed-off-by: Neal Gompa <neal@gompa.dev> --- Documentation/Subpage.rst | 15 ++++++++------- Documentation/mkfs.btrfs.rst | 13 +++++++++---- mkfs/main.c | 2 +- 3 files changed, 18 insertions(+), 12 deletions(-)