There were a few broken links for quota. The page https://ext4.wiki.kernel.org/index.php/Quota was not migrated into the current documentation sources. This patch adds the contents of that missing page as a new section in the overview page. Also fixes those broken links by replacing them with cross document links to this new quota section. Signed-off-by: Ayush Ranjan <ayushr2@xxxxxxxxxxxx> --- Documentation/filesystems/ext4/overview.rst | 1 + Documentation/filesystems/ext4/quota.rst | 53 +++++++++++++++++++++ Documentation/filesystems/ext4/super.rst | 6 +-- 3 files changed, 57 insertions(+), 3 deletions(-) create mode 100644 Documentation/filesystems/ext4/quota.rst diff --git a/Documentation/filesystems/ext4/overview.rst b/Documentation/filesystems/ext4/overview.rst index cbab18bab..f97ea68ea 100644 --- a/Documentation/filesystems/ext4/overview.rst +++ b/Documentation/filesystems/ext4/overview.rst @@ -24,3 +24,4 @@ order. .. include:: bigalloc.rst .. include:: inlinedata.rst .. include:: eainode.rst +.. include:: quota.rst diff --git a/Documentation/filesystems/ext4/quota.rst b/Documentation/filesystems/ext4/quota.rst new file mode 100644 index 000000000..8964c26cb --- /dev/null +++ b/Documentation/filesystems/ext4/quota.rst @@ -0,0 +1,53 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _quota: + +Quota Feature +------------- + +The quota feature (``EXT4_FEATURE_RO_COMPAT_QUOTA``) causes the quota +files (i.e., user.quota and group.quota which existed in the older quota +design) to be hidden inodes, so they can not be corrupted by user space +programs. Instead, these inodes are managed directly via e2fsprogs, and +journaled quota will be automatically enabled by the kernel as soon as +the file system is mounted. This way, it strongly reduces the +possibility that the usage tracking performed by the file system will +get out of sync. + +Kernel Support +~~~~~~~~~~~~~~ + +Support for the quota feature first appeared in the 3.6 upstream kernel +version. There is a bug which will not be fixed until v3.8 which will +cause ext4 to fail to mount a file system with quotas if the quota code +is built as a module. So users who wish to experiment with this feature +are strongly encouraged to build with the following configuration +options: + +- ``CONFIG_QUOTA=y`` +- ``CONFIG_QUOTATREE=y`` +- ``CONFIG_QUOTACTL=y`` + +E2fsprogs Support +~~~~~~~~~~~~~~~~~ + +Support for the quota feature first appeared in e2fsprogs 1.42, although +it is not enabled by default. It must enabled via a compile-time +configuration option, --enable-quota. There are bug fixes which have +been applied in various 1.42.x maintenance branch releases, so users who +wish to experiment with the quota feature are strongly encouraged +upgrade to the latest e2fsprogs 1.42.x maintenance release. As of this +writing the following bugs are still in e2fsprogs 1.42.7, which means +use of file systems with the quota feature in production can not be +recommended: + +- The e2fsck check of the on-disk quota inodes won't notice if there is + a missing uid record. (i.e., if some uid, say daemon owns a bunch of + files, but that uid record is not in the quota inode, e2fsck won't say + boo.) +- If e2fsck *does* notice a discrepancy between the usage information + recorded in the hidden quota inodes, and the actual number of blocks + used by a particular user id or group id, it will overwrite the user + or group quota inode with all of the information it has. + Unfortunately, in the process it will zero out all of the current + quota limits set. This is unfortunate.... diff --git a/Documentation/filesystems/ext4/super.rst b/Documentation/filesystems/ext4/super.rst index 04ff079a2..2a9e1438f 100644 --- a/Documentation/filesystems/ext4/super.rst +++ b/Documentation/filesystems/ext4/super.rst @@ -404,11 +404,11 @@ The ext4 superblock is laid out as follows in * - 0x240 - \_\_le32 - s\_usr\_quota\_inum - - Inode number of user `quota <quota>`__ file. + - Inode number of user :ref:`quota <quota>` file. * - 0x244 - \_\_le32 - s\_grp\_quota\_inum - - Inode number of group `quota <quota>`__ file. + - Inode number of group :ref:`quota <quota>` file. * - 0x248 - \_\_le32 - s\_overhead\_blocks @@ -678,7 +678,7 @@ the following: * - 0x80 - This filesystem has a snapshot (RO\_COMPAT\_HAS\_SNAPSHOT). * - 0x100 - - `Quota <Quota>`__ (RO\_COMPAT\_QUOTA). + - :ref:`Quota <quota>` (RO\_COMPAT\_QUOTA). * - 0x200 - This filesystem supports “bigalloc”, which means that file extents are tracked in units of clusters (of blocks) instead of blocks -- 2.23.0
