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| author | Kees Cook <kees+treewide@kernel.org> | 2026-09-02 15:31:14 -0700 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2026-09-04 21:37:00 -0700 |
| commit | 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d (patch) | |
| tree | c65086f9bdcd48c6360fb7cb4598bca084da1f32 /Documentation/filesystems/quota.rst | |
| download | linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.tar.gz linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.zip | |
treewide: refresh kmalloc_obj() conversionsgrafted
This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci
This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.
Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.
Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
Diffstat (limited to 'Documentation/filesystems/quota.rst')
| -rw-r--r-- | Documentation/filesystems/quota.rst | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/Documentation/filesystems/quota.rst b/Documentation/filesystems/quota.rst new file mode 100644 index 000000000..abd4303c5 --- /dev/null +++ b/Documentation/filesystems/quota.rst @@ -0,0 +1,85 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Quota subsystem +=============== + +Quota subsystem allows system administrator to set limits on used space and +number of used inodes (inode is a filesystem structure which is associated with +each file or directory) for users and/or groups. For both used space and number +of used inodes there are actually two limits. The first one is called softlimit +and the second one hardlimit. A user can never exceed a hardlimit for any +resource (unless he has CAP_SYS_RESOURCE capability). User is allowed to exceed +softlimit but only for limited period of time. This period is called "grace +period" or "grace time". When grace time is over, user is not able to allocate +more space/inodes until he frees enough of them to get below softlimit. + +Quota limits (and amount of grace time) are set independently for each +filesystem. + +For more details about quota design, see the documentation in quota-tools package +(https://sourceforge.net/projects/linuxquota). + +Quota netlink interface +======================= +When user exceeds a softlimit, runs out of grace time or reaches hardlimit, +quota subsystem traditionally printed a message to the controlling terminal of +the process which caused the excess. This method has the disadvantage that +when user is using a graphical desktop he usually cannot see the message. +Thus quota netlink interface has been designed to pass information about +the above events to userspace. There they can be captured by an application +and processed accordingly. + +The interface uses generic netlink framework (see +https://lwn.net/Articles/208755/ and http://www.infradead.org/~tgr/libnl/ for +more details about this layer). The name of the quota generic netlink interface +is "VFS_DQUOT". Definitions of constants below are in <linux/quota.h>. Since +the quota netlink protocol is not namespace aware, quota netlink messages are +sent only in initial network namespace. + +Currently, the interface supports only one message type QUOTA_NL_C_WARNING. +This command is used to send a notification about any of the above mentioned +events. Each message has six attributes. These are (type of the argument is +in parentheses): + + QUOTA_NL_A_QTYPE (u32) + - type of quota being exceeded (one of USRQUOTA, GRPQUOTA) + QUOTA_NL_A_EXCESS_ID (u64) + - UID/GID (depends on quota type) of user / group whose limit + is being exceeded. + QUOTA_NL_A_CAUSED_ID (u64) + - UID of a user who caused the event + QUOTA_NL_A_WARNING (u32) + - what kind of limit is exceeded: + + QUOTA_NL_IHARDWARN + inode hardlimit + QUOTA_NL_ISOFTLONGWARN + inode softlimit is exceeded longer + than given grace period + QUOTA_NL_ISOFTWARN + inode softlimit + QUOTA_NL_BHARDWARN + space (block) hardlimit + QUOTA_NL_BSOFTLONGWARN + space (block) softlimit is exceeded + longer than given grace period. + QUOTA_NL_BSOFTWARN + space (block) softlimit + + - four warnings are also defined for the event when user stops + exceeding some limit: + + QUOTA_NL_IHARDBELOW + inode hardlimit + QUOTA_NL_ISOFTBELOW + inode softlimit + QUOTA_NL_BHARDBELOW + space (block) hardlimit + QUOTA_NL_BSOFTBELOW + space (block) softlimit + + QUOTA_NL_A_DEV_MAJOR (u32) + - major number of a device with the affected filesystem + QUOTA_NL_A_DEV_MINOR (u32) + - minor number of a device with the affected filesystem |
