From 4d8199f0e3d30be69ebd10820d5402ec8d326e38 Mon Sep 17 00:00:00 2001 From: Neal Gompa Date: Wed, 22 Mar 2023 18:17:14 -0400 Subject: [PATCH 1/1] btrfs-progs: mkfs: Enforce 4k sectorsize by default 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 Reviewed-by: Anand Jain Reviewed-by: Qu Wenruo Reviewed-by: Josef Bacik --- Documentation/Subpage.rst | 17 +++++++++-------- Documentation/mkfs.btrfs.rst | 13 +++++++++---- mkfs/main.c | 2 +- 3 files changed, 19 insertions(+), 13 deletions(-) diff --git a/Documentation/Subpage.rst b/Documentation/Subpage.rst index c762b6a3..4bcfc6cf 100644 --- a/Documentation/Subpage.rst +++ b/Documentation/Subpage.rst @@ -9,18 +9,19 @@ 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 -and mount filesystems with 4KiB sectorsize. This still needs to use option "-s -4k" option for :command:`mkfs.btrfs`. +Since v6.5, 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 :command:`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, most features are already working without problems. -On a 64KiB page system filesystem with 4KiB sectorsize can be mounted and used -as usual as long as the initial mount succeeds. There are cases a mount will be -rejected when verifying compatible features. +The initial subpage support has been added in v5.15. Most features are +already working without problems. On a 64KiB page system, a filesystem with +4KiB sectorsize can be mounted and used as long as the initial mount succeeds. +Subpage support is used by default for systems with a non-4KiB page size since v6.5. Please refer to status page of :ref:`status-subpage-block-size` for compatibility. diff --git a/Documentation/mkfs.btrfs.rst b/Documentation/mkfs.btrfs.rst index 1fca7448..d602fe9c 100644 --- a/Documentation/mkfs.btrfs.rst +++ b/Documentation/mkfs.btrfs.rst @@ -122,10 +122,15 @@ OPTIONS -s|--sectorsize 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 6.4 set the sectorsize matching to the page size. -L|--label Specify a label for the filesystem. The *string* should be less than 256 diff --git a/mkfs/main.c b/mkfs/main.c index 1c5d668e..bd2e4350 100644 --- a/mkfs/main.c +++ b/mkfs/main.c @@ -1204,7 +1204,7 @@ 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; -- 2.41.0