shmem: quota support

Now the basic infra-structure is in place, enable quota support for tmpfs.

This offers user and group quotas to tmpfs (project quotas will be added
later). Also, as other filesystems, the tmpfs quota is not supported
within user namespaces yet, so idmapping is not translated.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230725144510.253763-6-cem@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Documentation/filesystems/tmpfs.rst

@@ -123,6 +123,21 @@ sysfs file /sys/kernel/mm/transparent_hugepage/shmem_enabled: which can
 be used to deny huge pages on all tmpfs mounts in an emergency, or to
 force huge pages on all tmpfs mounts for testing.
 
+tmpfs also supports quota with the following mount options
+
+========  =============================================================
+quota     User and group quota accounting and enforcement is enabled on
+          the mount. Tmpfs is using hidden system quota files that are
+          initialized on mount.
+usrquota  User quota accounting and enforcement is enabled on the
+          mount.
+grpquota  Group quota accounting and enforcement is enabled on the
+          mount.
+========  =============================================================
+
+Note that tmpfs quotas do not support user namespaces so no uid/gid
+translation is done if quotas are enabled inside user namespaces.
+
 tmpfs has a mount option to set the NUMA memory allocation policy for
 all files in that instance (if CONFIG_NUMA is enabled) - which can be
 adjusted on the fly via 'mount -o remount ...'

include/linux/shmem_fs.h

@@ -31,6 +31,9 @@ struct shmem_inode_info {
 	atomic_t		stop_eviction;	/* hold when working on inode */
 	struct timespec64	i_crtime;	/* file creation time */
 	unsigned int		fsflags;	/* flags for FS_IOC_[SG]ETFLAGS */
+#ifdef CONFIG_TMPFS_QUOTA
+	struct dquot		*i_dquot[MAXQUOTAS];
+#endif
 	struct inode		vfs_inode;
 };
 
@@ -184,4 +187,9 @@ extern int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 #define SHMEM_QUOTA_MAX_SPC_LIMIT 0x7fffffffffffffffLL /* 2^63-1 */
 #define SHMEM_QUOTA_MAX_INO_LIMIT 0x7fffffffffffffffLL
 
+#ifdef CONFIG_TMPFS_QUOTA
+extern const struct dquot_operations shmem_quota_operations;
+extern struct quota_format_type shmem_quota_format;
+#endif /* CONFIG_TMPFS_QUOTA */
+
 #endif

mm/shmem.c

@@ -78,6 +78,7 @@ static struct vfsmount *shm_mnt;
 #include <uapi/linux/memfd.h>
 #include <linux/rmap.h>
 #include <linux/uuid.h>
+#include <linux/quotaops.h>
 
 #include <linux/uaccess.h>
 
@@ -116,11 +117,13 @@ struct shmem_options {
 	int huge;
 	int seen;
 	bool noswap;
+	unsigned short quota_types;
 #define SHMEM_SEEN_BLOCKS 1
 #define SHMEM_SEEN_INODES 2
 #define SHMEM_SEEN_HUGE 4
 #define SHMEM_SEEN_INUMS 8
 #define SHMEM_SEEN_NOSWAP 16
+#define SHMEM_SEEN_QUOTA 32
 };
 
 #ifdef CONFIG_TMPFS
@@ -212,7 +215,16 @@ static inline int shmem_inode_acct_block(struct inode *inode, long pages)
 		if (percpu_counter_compare(&sbinfo->used_blocks,
 					   sbinfo->max_blocks - pages) > 0)
 			goto unacct;
+
+		err = dquot_alloc_block_nodirty(inode, pages);
+		if (err)
+			goto unacct;
+
 		percpu_counter_add(&sbinfo->used_blocks, pages);
+	} else {
+		err = dquot_alloc_block_nodirty(inode, pages);
+		if (err)
+			goto unacct;
 	}
 
 	return 0;
@@ -227,6 +239,8 @@ static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
+	dquot_free_block_nodirty(inode, pages);
+
 	if (sbinfo->max_blocks)
 		percpu_counter_sub(&sbinfo->used_blocks, pages);
 	shmem_unacct_blocks(info->flags, pages);
@@ -255,6 +269,47 @@ bool vma_is_shmem(struct vm_area_struct *vma)
 static LIST_HEAD(shmem_swaplist);
 static DEFINE_MUTEX(shmem_swaplist_mutex);
 
+#ifdef CONFIG_TMPFS_QUOTA
+
+static int shmem_enable_quotas(struct super_block *sb,
+			       unsigned short quota_types)
+{
+	int type, err = 0;
+
+	sb_dqopt(sb)->flags |= DQUOT_QUOTA_SYS_FILE | DQUOT_NOLIST_DIRTY;
+	for (type = 0; type < SHMEM_MAXQUOTAS; type++) {
+		if (!(quota_types & (1 << type)))
+			continue;
+		err = dquot_load_quota_sb(sb, type, QFMT_SHMEM,
+					  DQUOT_USAGE_ENABLED |
+					  DQUOT_LIMITS_ENABLED);
+		if (err)
+			goto out_err;
+	}
+	return 0;
+
+out_err:
+	pr_warn("tmpfs: failed to enable quota tracking (type=%d, err=%d)\n",
+		type, err);
+	for (type--; type >= 0; type--)
+		dquot_quota_off(sb, type);
+	return err;
+}
+
+static void shmem_disable_quotas(struct super_block *sb)
+{
+	int type;
+
+	for (type = 0; type < SHMEM_MAXQUOTAS; type++)
+		dquot_quota_off(sb, type);
+}
+
+static struct dquot **shmem_get_dquots(struct inode *inode)
+{
+	return SHMEM_I(inode)->i_dquot;
+}
+#endif /* CONFIG_TMPFS_QUOTA */
+
 /*
  * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
  * produces a novel ino for the newly allocated inode.
@@ -361,7 +416,6 @@ static void shmem_recalc_inode(struct inode *inode)
 	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 	if (freed > 0) {
 		info->alloced -= freed;
-		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
 		shmem_inode_unacct_blocks(inode, freed);
 	}
 }
@@ -379,7 +433,6 @@ bool shmem_charge(struct inode *inode, long pages)
 
 	spin_lock_irqsave(&info->lock, flags);
 	info->alloced += pages;
-	inode->i_blocks += pages * BLOCKS_PER_PAGE;
 	shmem_recalc_inode(inode);
 	spin_unlock_irqrestore(&info->lock, flags);
 
@@ -395,7 +448,6 @@ void shmem_uncharge(struct inode *inode, long pages)
 
 	spin_lock_irqsave(&info->lock, flags);
 	info->alloced -= pages;
-	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
 	shmem_recalc_inode(inode);
 	spin_unlock_irqrestore(&info->lock, flags);
 
@@ -1141,6 +1193,21 @@ static int shmem_setattr(struct mnt_idmap *idmap,
 		}
 	}
 
+	if (is_quota_modification(idmap, inode, attr)) {
+		error = dquot_initialize(inode);
+		if (error)
+			return error;
+	}
+
+	/* Transfer quota accounting */
+	if (i_uid_needs_update(idmap, attr, inode) ||
+	    i_gid_needs_update(idmap, attr, inode)) {
+		error = dquot_transfer(idmap, inode, attr);
+
+		if (error)
+			return error;
+	}
+
 	setattr_copy(idmap, inode, attr);
 	if (attr->ia_valid & ATTR_MODE)
 		error = posix_acl_chmod(idmap, dentry, inode->i_mode);
@@ -1187,6 +1254,10 @@ static void shmem_evict_inode(struct inode *inode)
 	WARN_ON(inode->i_blocks);
 	shmem_free_inode(inode->i_sb);
 	clear_inode(inode);
+#ifdef CONFIG_TMPFS_QUOTA
+	dquot_free_inode(inode);
+	dquot_drop(inode);
+#endif
 }
 
 static int shmem_find_swap_entries(struct address_space *mapping,
@@ -1986,7 +2057,6 @@ alloc_nohuge:
 
 	spin_lock_irq(&info->lock);
 	info->alloced += folio_nr_pages(folio);
-	inode->i_blocks += (blkcnt_t)BLOCKS_PER_PAGE << folio_order(folio);
 	shmem_recalc_inode(inode);
 	spin_unlock_irq(&info->lock);
 	alloced = true;
@@ -2357,9 +2427,10 @@ static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
 #define shmem_initxattrs NULL
 #endif
 
-static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block *sb,
-				     struct inode *dir, umode_t mode, dev_t dev,
-				     unsigned long flags)
+static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
+					     struct super_block *sb,
+					     struct inode *dir, umode_t mode,
+					     dev_t dev, unsigned long flags)
 {
 	struct inode *inode;
 	struct shmem_inode_info *info;
@@ -2436,6 +2507,43 @@ static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block
 	return inode;
 }
 
+#ifdef CONFIG_TMPFS_QUOTA
+static struct inode *shmem_get_inode(struct mnt_idmap *idmap,
+				     struct super_block *sb, struct inode *dir,
+				     umode_t mode, dev_t dev, unsigned long flags)
+{
+	int err;
+	struct inode *inode;
+
+	inode = __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
+	if (IS_ERR(inode))
+		return inode;
+
+	err = dquot_initialize(inode);
+	if (err)
+		goto errout;
+
+	err = dquot_alloc_inode(inode);
+	if (err) {
+		dquot_drop(inode);
+		goto errout;
+	}
+	return inode;
+
+errout:
+	inode->i_flags |= S_NOQUOTA;
+	iput(inode);
+	return ERR_PTR(err);
+}
+#else
+static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
+				     struct super_block *sb, struct inode *dir,
+				     umode_t mode, dev_t dev, unsigned long flags)
+{
+	return __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
+}
+#endif /* CONFIG_TMPFS_QUOTA */
+
 #ifdef CONFIG_USERFAULTFD
 int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 			   struct vm_area_struct *dst_vma,
@@ -2538,7 +2646,6 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 
 	spin_lock_irq(&info->lock);
 	info->alloced++;
-	inode->i_blocks += BLOCKS_PER_PAGE;
 	shmem_recalc_inode(inode);
 	spin_unlock_irq(&info->lock);
 
@@ -3519,6 +3626,7 @@ static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
 
 static const struct inode_operations shmem_short_symlink_operations = {
 	.getattr	= shmem_getattr,
+	.setattr	= shmem_setattr,
 	.get_link	= simple_get_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
@@ -3527,6 +3635,7 @@ static const struct inode_operations shmem_short_symlink_operations = {
 
 static const struct inode_operations shmem_symlink_inode_operations = {
 	.getattr	= shmem_getattr,
+	.setattr	= shmem_setattr,
 	.get_link	= shmem_get_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
@@ -3626,6 +3735,9 @@ enum shmem_param {
 	Opt_inode32,
 	Opt_inode64,
 	Opt_noswap,
+	Opt_quota,
+	Opt_usrquota,
+	Opt_grpquota,
 };
 
 static const struct constant_table shmem_param_enums_huge[] = {
@@ -3648,6 +3760,11 @@ const struct fs_parameter_spec shmem_fs_parameters[] = {
 	fsparam_flag  ("inode32",	Opt_inode32),
 	fsparam_flag  ("inode64",	Opt_inode64),
 	fsparam_flag  ("noswap",	Opt_noswap),
+#ifdef CONFIG_TMPFS_QUOTA
+	fsparam_flag  ("quota",		Opt_quota),
+	fsparam_flag  ("usrquota",	Opt_usrquota),
+	fsparam_flag  ("grpquota",	Opt_grpquota),
+#endif
 	{}
 };
 
@@ -3739,6 +3856,24 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 		ctx->noswap = true;
 		ctx->seen |= SHMEM_SEEN_NOSWAP;
 		break;
+	case Opt_quota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= (QTYPE_MASK_USR | QTYPE_MASK_GRP);
+		break;
+	case Opt_usrquota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= QTYPE_MASK_USR;
+		break;
+	case Opt_grpquota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= QTYPE_MASK_GRP;
+		break;
 	}
 	return 0;
 
@@ -3846,6 +3981,12 @@ static int shmem_reconfigure(struct fs_context *fc)
 		goto out;
 	}
 
+	if (ctx->seen & SHMEM_SEEN_QUOTA &&
+	    !sb_any_quota_loaded(fc->root->d_sb)) {
+		err = "Cannot enable quota on remount";
+		goto out;
+	}
+
 	if (ctx->seen & SHMEM_SEEN_HUGE)
 		sbinfo->huge = ctx->huge;
 	if (ctx->seen & SHMEM_SEEN_INUMS)
@@ -3937,6 +4078,9 @@ static void shmem_put_super(struct super_block *sb)
 {
 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 
+#ifdef CONFIG_TMPFS_QUOTA
+	shmem_disable_quotas(sb);
+#endif
 	free_percpu(sbinfo->ino_batch);
 	percpu_counter_destroy(&sbinfo->used_blocks);
 	mpol_put(sbinfo->mpol);
@@ -4016,6 +4160,17 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 #endif
 	uuid_gen(&sb->s_uuid);
 
+#ifdef CONFIG_TMPFS_QUOTA
+	if (ctx->seen & SHMEM_SEEN_QUOTA) {
+		sb->dq_op = &shmem_quota_operations;
+		sb->s_qcop = &dquot_quotactl_sysfile_ops;
+		sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP;
+
+		if (shmem_enable_quotas(sb, ctx->quota_types))
+			goto failed;
+	}
+#endif /* CONFIG_TMPFS_QUOTA */
+
 	inode = shmem_get_inode(&nop_mnt_idmap, sb, NULL, S_IFDIR | sbinfo->mode, 0,
 				VM_NORESERVE);
 	if (IS_ERR(inode)) {
@@ -4191,6 +4346,9 @@ static const struct super_operations shmem_ops = {
 #ifdef CONFIG_TMPFS
 	.statfs		= shmem_statfs,
 	.show_options	= shmem_show_options,
+#endif
+#ifdef CONFIG_TMPFS_QUOTA
+	.get_dquots	= shmem_get_dquots,
 #endif
 	.evict_inode	= shmem_evict_inode,
 	.drop_inode	= generic_delete_inode,
@@ -4257,6 +4415,14 @@ void __init shmem_init(void)
 
 	shmem_init_inodecache();
 
+#ifdef CONFIG_TMPFS_QUOTA
+	error = register_quota_format(&shmem_quota_format);
+	if (error < 0) {
+		pr_err("Could not register quota format\n");
+		goto out3;
+	}
+#endif
+
 	error = register_filesystem(&shmem_fs_type);
 	if (error) {
 		pr_err("Could not register tmpfs\n");
@@ -4281,6 +4447,10 @@ void __init shmem_init(void)
 out1:
 	unregister_filesystem(&shmem_fs_type);
 out2:
+#ifdef CONFIG_TMPFS_QUOTA
+	unregister_quota_format(&shmem_quota_format);
+out3:
+#endif
 	shmem_destroy_inodecache();
 	shm_mnt = ERR_PTR(error);
 }