From: Carlos Maiolino <cem@xxxxxxxxxx>
Add new shmem quota format, its quota_format_ops together with
dquot_operations
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
---
fs/Kconfig | 12 ++
include/linux/shmem_fs.h | 12 ++
include/uapi/linux/quota.h | 1 +
mm/Makefile | 2 +-
mm/shmem_quota.c | 318 +++++++++++++++++++++++++++++++++++++
5 files changed, 344 insertions(+), 1 deletion(-)
create mode 100644 mm/shmem_quota.c
diff --git a/fs/Kconfig b/fs/Kconfig
index 18d034ec7953..8218a71933f9 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -233,6 +233,18 @@ config TMPFS_INODE64
If unsure, say N.
+config TMPFS_QUOTA
+ bool "Tmpfs quota support"
+ depends on TMPFS
+ select QUOTA
+ help
+ Quota support allows to set per user and group limits for tmpfs
+ usage. Say Y to enable quota support. Once enabled you can control
+ user and group quota enforcement with quota, usrquota and grpquota
+ mount options.
+
+ If unsure, say N.
+
config ARCH_SUPPORTS_HUGETLBFS
def_bool n
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 9029abd29b1c..7abfaf70b58a 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -13,6 +13,10 @@
/* inode in-kernel data */
+#ifdef CONFIG_TMPFS_QUOTA
+#define SHMEM_MAXQUOTAS 2
+#endif
+
struct shmem_inode_info {
spinlock_t lock;
unsigned int seals; /* shmem seals */
@@ -172,4 +176,12 @@ extern int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
#endif /* CONFIG_SHMEM */
#endif /* CONFIG_USERFAULTFD */
+/*
+ * Used space is stored as unsigned 64-bit value in bytes but
+ * quota core supports only signed 64-bit values so use that
+ * as a limit
+ */
+#define SHMEM_QUOTA_MAX_SPC_LIMIT 0x7fffffffffffffffLL /* 2^63-1 */
+#define SHMEM_QUOTA_MAX_INO_LIMIT 0x7fffffffffffffffLL
+
#endif
diff --git a/include/uapi/linux/quota.h b/include/uapi/linux/quota.h
index f17c9636a859..52090105b828 100644
--- a/include/uapi/linux/quota.h
+++ b/include/uapi/linux/quota.h
@@ -77,6 +77,7 @@
#define QFMT_VFS_V0 2
#define QFMT_OCFS2 3
#define QFMT_VFS_V1 4
+#define QFMT_SHMEM 5
/* Size of block in which space limits are passed through the quota
* interface */
diff --git a/mm/Makefile b/mm/Makefile
index 678530a07326..d4ee20988dd1 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -51,7 +51,7 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
readahead.o swap.o truncate.o vmscan.o shmem.o \
util.o mmzone.o vmstat.o backing-dev.o \
mm_init.o percpu.o slab_common.o \
- compaction.o show_mem.o\
+ compaction.o show_mem.o shmem_quota.o\
interval_tree.o list_lru.o workingset.o \
debug.o gup.o mmap_lock.o $(mmu-y)
diff --git a/mm/shmem_quota.c b/mm/shmem_quota.c
new file mode 100644
index 000000000000..e92b8ece9880
--- /dev/null
+++ b/mm/shmem_quota.c
@@ -0,0 +1,318 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * In memory quota format relies on quota infrastructure to store dquot
+ * information for us. While conventional quota formats for file systems
+ * with persistent storage can load quota information into dquot from the
+ * storage on-demand and hence quota dquot shrinker can free any dquot
+ * that is not currently being used, it must be avoided here. Otherwise we
+ * can lose valuable information, user provided limits, because there is
+ * no persistent storage to load the information from afterwards.
+ *
+ * One information that in-memory quota format needs to keep track of is
+ * a sorted list of ids for each quota type. This is done by utilizing
+ * an rb tree which root is stored in mem_dqinfo->dqi_priv for each quota
+ * type.
+ *
+ * This format can be used to support quota on file system without persistent
+ * storage such as tmpfs.
+ *
+ * Author: Lukas Czerner <lczerner@xxxxxxxxxx>
+ * Carlos Maiolino <cmaiolino@xxxxxxxxxx>
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ */
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+#include <linux/shmem_fs.h>
+
+#include <linux/quotaops.h>
+#include <linux/quota.h>
+
+#ifdef CONFIG_TMPFS_QUOTA
+
+/*
+ * The following constants define the amount of time given a user
+ * before the soft limits are treated as hard limits (usually resulting
+ * in an allocation failure). The timer is started when the user crosses
+ * their soft limit, it is reset when they go below their soft limit.
+ */
+#define SHMEM_MAX_IQ_TIME 604800 /* (7*24*60*60) 1 week */
+#define SHMEM_MAX_DQ_TIME 604800 /* (7*24*60*60) 1 week */
+
+struct quota_id {
+ struct rb_node node;
+ qid_t id;
+ qsize_t bhardlimit;
+ qsize_t bsoftlimit;
+ qsize_t ihardlimit;
+ qsize_t isoftlimit;
+};
+
+static int shmem_check_quota_file(struct super_block *sb, int type)
+{
+ /* There is no real quota file, nothing to do */
+ return 1;
+}
+
+/*
+ * There is no real quota file. Just allocate rb_root for quota ids and
+ * set limits
+ */
+static int shmem_read_file_info(struct super_block *sb, int type)
+{
+ struct quota_info *dqopt = sb_dqopt(sb);
+ struct mem_dqinfo *info = &dqopt->info[type];
+
+ info->dqi_priv = kzalloc(sizeof(struct rb_root), GFP_NOFS);
+ if (!info->dqi_priv)
+ return -ENOMEM;
+
+ info->dqi_max_spc_limit = SHMEM_QUOTA_MAX_SPC_LIMIT;
+ info->dqi_max_ino_limit = SHMEM_QUOTA_MAX_INO_LIMIT;
+
+ info->dqi_bgrace = SHMEM_MAX_DQ_TIME;
+ info->dqi_igrace = SHMEM_MAX_IQ_TIME;
+ info->dqi_flags = 0;
+
+ return 0;
+}
+
+static int shmem_write_file_info(struct super_block *sb, int type)
+{
+ /* There is no real quota file, nothing to do */
+ return 0;
+}
+
+/*
+ * Free all the quota_id entries in the rb tree and rb_root.
+ */
+static int shmem_free_file_info(struct super_block *sb, int type)
+{
+ struct mem_dqinfo *info = &sb_dqopt(sb)->info[type];
+ struct rb_root *root = info->dqi_priv;
+ struct quota_id *entry;
+ struct rb_node *node;
+
+ info->dqi_priv = NULL;
+ node = rb_first(root);
+ while (node) {
+ entry = rb_entry(node, struct quota_id, node);
+ node = rb_next(&entry->node);
+
+ rb_erase(&entry->node, root);
+ kfree(entry);
+ }
+
+ kfree(root);
+ return 0;
+}
+
+static int shmem_get_next_id(struct super_block *sb, struct kqid *qid)
+{
+ struct mem_dqinfo *info = sb_dqinfo(sb, qid->type);
+ struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node;
+ qid_t id = from_kqid(&init_user_ns, *qid);
+ struct quota_info *dqopt = sb_dqopt(sb);
+ struct quota_id *entry = NULL;
+ int ret = 0;
+
+ if (!sb_has_quota_active(sb, qid->type))
+ return -ESRCH;
+
+ down_read(&dqopt->dqio_sem);
+ while (node) {
+ entry = rb_entry(node, struct quota_id, node);
+
+ if (id < entry->id)
+ node = node->rb_left;
+ else if (id > entry->id)
+ node = node->rb_right;
+ else
+ goto got_next_id;
+ }
+
+ if (!entry) {
+ ret = -ENOENT;
+ goto out_unlock;
+ }
+
+ if (id > entry->id) {
+ node = rb_next(&entry->node);
+ if (!node) {
+ ret = -ENOENT;
+ goto out_unlock;
+ }
+ entry = rb_entry(node, struct quota_id, node);
+ }
+
+got_next_id:
+ *qid = make_kqid(&init_user_ns, qid->type, entry->id);
+out_unlock:
+ up_read(&dqopt->dqio_sem);
+ return ret;
+}
+
+/*
+ * Load dquot with limits from existing entry, or create the new entry if
+ * it does not exist.
+ */
+static int shmem_acquire_dquot(struct dquot *dquot)
+{
+ struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
+ struct rb_node **n = &((struct rb_root *)info->dqi_priv)->rb_node;
+ struct rb_node *parent = NULL, *new_node = NULL;
+ struct quota_id *new_entry, *entry;
+ qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
+ struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
+ int ret = 0;
+
+ mutex_lock(&dquot->dq_lock);
+
+ down_write(&dqopt->dqio_sem);
+ while (*n) {
+ parent = *n;
+ entry = rb_entry(parent, struct quota_id, node);
+
+ if (id < entry->id)
+ n = &(*n)->rb_left;
+ else if (id > entry->id)
+ n = &(*n)->rb_right;
+ else
+ goto found;
+ }
+
+ /* We don't have entry for this id yet, create it */
+ new_entry = kzalloc(sizeof(struct quota_id), GFP_NOFS);
+ if (!new_entry) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ new_entry->id = id;
+ new_node = &new_entry->node;
+ rb_link_node(new_node, parent, n);
+ rb_insert_color(new_node, (struct rb_root *)info->dqi_priv);
+ entry = new_entry;
+
+found:
+ /* Load the stored limits from the tree */
+ spin_lock(&dquot->dq_dqb_lock);
+ dquot->dq_dqb.dqb_bhardlimit = entry->bhardlimit;
+ dquot->dq_dqb.dqb_bsoftlimit = entry->bsoftlimit;
+ dquot->dq_dqb.dqb_ihardlimit = entry->ihardlimit;
+ dquot->dq_dqb.dqb_isoftlimit = entry->isoftlimit;
+
+ if (!dquot->dq_dqb.dqb_bhardlimit &&
+ !dquot->dq_dqb.dqb_bsoftlimit &&
+ !dquot->dq_dqb.dqb_ihardlimit &&
+ !dquot->dq_dqb.dqb_isoftlimit)
+ set_bit(DQ_FAKE_B, &dquot->dq_flags);
+ spin_unlock(&dquot->dq_dqb_lock);
+
+ /* Make sure flags update is visible after dquot has been filled */
+ smp_mb__before_atomic();
+ set_bit(DQ_ACTIVE_B, &dquot->dq_flags);
+out_unlock:
+ up_write(&dqopt->dqio_sem);
+ mutex_unlock(&dquot->dq_lock);
+ return ret;
+}
+
+/*
+ * Store limits from dquot in the tree unless it's fake. If it is fake
+ * remove the id from the tree since there is no useful information in
+ * there.
+ */
+static int shmem_release_dquot(struct dquot *dquot)
+{
+ struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
+ struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node;
+ qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
+ struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
+ struct quota_id *entry = NULL;
+
+ mutex_lock(&dquot->dq_lock);
+ /* Check whether we are not racing with some other dqget() */
+ if (dquot_is_busy(dquot))
+ goto out_dqlock;
+
+ down_write(&dqopt->dqio_sem);
+ while (node) {
+ entry = rb_entry(node, struct quota_id, node);
+
+ if (id < entry->id)
+ node = node->rb_left;
+ else if (id > entry->id)
+ node = node->rb_right;
+ else
+ goto found;
+ }
+
+ /* We should always find the entry in the rb tree */
+ WARN_ONCE(1, "quota id %u from dquot %p, not in rb tree!\n", id, dquot);
+ up_write(&dqopt->dqio_sem);
+ mutex_unlock(&dquot->dq_lock);
+ return -ENOENT;
+
+found:
+ if (test_bit(DQ_FAKE_B, &dquot->dq_flags)) {
+ /* Remove entry from the tree */
+ rb_erase(&entry->node, info->dqi_priv);
+ kfree(entry);
+ } else {
+ /* Store the limits in the tree */
+ spin_lock(&dquot->dq_dqb_lock);
+ entry->bhardlimit = dquot->dq_dqb.dqb_bhardlimit;
+ entry->bsoftlimit = dquot->dq_dqb.dqb_bsoftlimit;
+ entry->ihardlimit = dquot->dq_dqb.dqb_ihardlimit;
+ entry->isoftlimit = dquot->dq_dqb.dqb_isoftlimit;
+ spin_unlock(&dquot->dq_dqb_lock);
+ }
+
+ clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
+ up_write(&dqopt->dqio_sem);
+
+out_dqlock:
+ mutex_unlock(&dquot->dq_lock);
+ return 0;
+}
+
+static int shmem_mark_dquot_dirty(struct dquot *dquot)
+{
+ return 0;
+}
+
+static int shmem_dquot_write_info(struct super_block *sb, int type)
+{
+ return 0;
+}
+
+static const struct quota_format_ops shmem_format_ops = {
+ .check_quota_file = shmem_check_quota_file,
+ .read_file_info = shmem_read_file_info,
+ .write_file_info = shmem_write_file_info,
+ .free_file_info = shmem_free_file_info,
+};
+
+struct quota_format_type shmem_quota_format = {
+ .qf_fmt_id = QFMT_SHMEM,
+ .qf_ops = &shmem_format_ops,
+ .qf_owner = THIS_MODULE
+};
+
+const struct dquot_operations shmem_quota_operations = {
+ .acquire_dquot = shmem_acquire_dquot,
+ .release_dquot = shmem_release_dquot,
+ .alloc_dquot = dquot_alloc,
+ .destroy_dquot = dquot_destroy,
+ .write_info = shmem_dquot_write_info,
+ .mark_dirty = shmem_mark_dquot_dirty,
+ .get_next_id = shmem_get_next_id,
+};
+#endif /* CONFIG_TMPFS_QUOTA */
--
2.39.2
