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Date: Wed, 11 Feb 2015 15:50:08 +0100
From: Krzysztof Kozlowski <k.kozlowski@...sung.com>
To: Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org
Cc: Kyungmin Park <kyungmin.park@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [RFC] shmem: Add eventfd notification on utlilization level
Allow notifying user space when used space of tmpfs exceeds specified
level.
The utilization level is passed as mount option 'warn_used'. The kernel
will notify user-space through eventfd after exceeding this number of
used blocks.
The eventfd descriptor has to be passed through sysfs file:
/sys/fs/tmpfs/tmpfs-[0-9]+/warn_used_blocks_efd
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
---
include/linux/shmem_fs.h | 4 ++
mm/shmem.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 140 insertions(+), 2 deletions(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 50777b5b1e4c..c2ec9909da95 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -35,6 +35,10 @@ struct shmem_sb_info {
kgid_t gid; /* Mount gid for root directory */
umode_t mode; /* Mount mode for root directory */
struct mempolicy *mpol; /* default memory policy for mappings */
+ unsigned long warn_used; /* Warn on reaching used blocks */
+ struct kobject s_kobj; /* kobj for sysfs attributes */
+ struct completion s_kobj_unregister; /* synchronization for put_super */
+ struct eventfd_ctx *warn_used_efd; /* user-space passed eventfd */
};
static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
diff --git a/mm/shmem.c b/mm/shmem.c
index f69d296bd0a3..b559adcef3b3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -34,6 +34,7 @@
#include <linux/aio.h>
static struct vfsmount *shm_mnt;
+static struct kset *shmem_kset;
#ifdef CONFIG_SHMEM
/*
@@ -69,6 +70,7 @@ static struct vfsmount *shm_mnt;
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <uapi/linux/memfd.h>
+#include <linux/eventfd.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -199,6 +201,106 @@ static struct backing_dev_info shmem_backing_dev_info __read_mostly = {
static LIST_HEAD(shmem_swaplist);
static DEFINE_MUTEX(shmem_swaplist_mutex);
+
+struct shmem_attr {
+ struct attribute attr;
+ ssize_t (*show)(struct shmem_attr *, struct shmem_sb_info *, char *);
+ ssize_t (*store)(struct shmem_attr *, struct shmem_sb_info *,
+ const char *, size_t);
+};
+
+static int shmem_setup_warn_used_blocks_eventfd(struct shmem_sb_info *sbinfo,
+ unsigned int efd)
+{
+ int ret = 0;
+
+ if (sbinfo->warn_used_efd) {
+ eventfd_ctx_put(sbinfo->warn_used_efd);
+ sbinfo->warn_used_efd = NULL;
+ }
+
+ sbinfo->warn_used_efd = eventfd_ctx_fdget(efd);
+ if (IS_ERR(sbinfo->warn_used_efd)) {
+ ret = PTR_ERR(sbinfo->warn_used_efd);
+ sbinfo->warn_used_efd = NULL;
+ }
+
+ return ret;
+}
+
+static int parse_strtouint(const char *buf,
+ unsigned long long max, unsigned int *value)
+{
+ int ret;
+
+ ret = kstrtouint(skip_spaces(buf), 0, value);
+ if (!ret && *value > max)
+ ret = -EINVAL;
+ return ret;
+}
+
+static ssize_t warn_used_blocks_efd_store(struct shmem_attr *a,
+ struct shmem_sb_info *sbinfo,
+ const char *buf, size_t count)
+{
+ unsigned int val;
+ int ret;
+
+ if (parse_strtouint(buf, -1ULL, &val))
+ return -EINVAL;
+
+ ret = shmem_setup_warn_used_blocks_eventfd(sbinfo, val);
+
+ return ret ? ret : count;
+}
+
+static struct shmem_attr
+shmem_attr_warn_used_blocks_efd = __ATTR_WO(warn_used_blocks_efd);
+
+static struct attribute *shmem_attrs[] = {
+ &shmem_attr_warn_used_blocks_efd.attr,
+ NULL,
+};
+
+static ssize_t shmem_attr_show(struct kobject *kobj,
+ struct attribute *attr, char *buf)
+{
+ struct shmem_sb_info *sbinfo = container_of(kobj, struct shmem_sb_info,
+ s_kobj);
+ struct shmem_attr *a = container_of(attr, struct shmem_attr, attr);
+
+ return a->show ? a->show(a, sbinfo, buf) : 0;
+}
+
+static ssize_t shmem_attr_store(struct kobject *kobj,
+ struct attribute *attr,
+ const char *buf, size_t len)
+{
+ struct shmem_sb_info *sbinfo = container_of(kobj, struct shmem_sb_info,
+ s_kobj);
+ struct shmem_attr *a = container_of(attr, struct shmem_attr, attr);
+
+ return a->store ? a->store(a, sbinfo, buf, len) : 0;
+}
+
+static void shmem_sb_release(struct kobject *kobj)
+{
+ struct shmem_sb_info *sbinfo = container_of(kobj, struct shmem_sb_info,
+ s_kobj);
+ complete(&sbinfo->s_kobj_unregister);
+}
+
+static const struct sysfs_ops shmem_attr_ops = {
+ .show = shmem_attr_show,
+ .store = shmem_attr_store,
+};
+
+static struct kobj_type shmem_ktype = {
+ .default_attrs = shmem_attrs,
+ .sysfs_ops = &shmem_attr_ops,
+ .release = shmem_sb_release,
+};
+
static int shmem_reserve_inode(struct super_block *sb)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
@@ -1170,6 +1272,13 @@ repeat:
}
percpu_counter_inc(&sbinfo->used_blocks);
}
+ if (sbinfo->warn_used) {
+ if (percpu_counter_compare(&sbinfo->used_blocks,
+ sbinfo->warn_used) >= 0) {
+ if (sbinfo->warn_used_efd)
+ eventfd_signal(sbinfo->warn_used_efd, 1);
+ }
+ }
page = shmem_alloc_page(gfp, info, index);
if (!page) {
@@ -2824,6 +2933,10 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
mpol = NULL;
if (mpol_parse_str(value, &mpol))
goto bad_val;
+ } else if (!strcmp(this_char,"warn_used")) {
+ sbinfo->warn_used = memparse(value, &rest);
+ if (*rest)
+ goto bad_val;
} else {
printk(KERN_ERR "tmpfs: Bad mount option %s\n",
this_char);
@@ -2984,6 +3097,13 @@ static void shmem_put_super(struct super_block *sb)
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
percpu_counter_destroy(&sbinfo->used_blocks);
+ if (sbinfo->warn_used_efd) {
+ eventfd_ctx_put(sbinfo->warn_used_efd);
+ sbinfo->warn_used_efd = NULL;
+ }
+ kobject_del(&sbinfo->s_kobj);
+ kobject_put(&sbinfo->s_kobj);
+ wait_for_completion(&sbinfo->s_kobj_unregister);
mpol_put(sbinfo->mpol);
kfree(sbinfo);
sb->s_fs_info = NULL;
@@ -2994,6 +3114,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
struct inode *inode;
struct shmem_sb_info *sbinfo;
int err = -ENOMEM;
+ static unsigned int no;
/* Round up to L1_CACHE_BYTES to resist false sharing */
sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
@@ -3045,17 +3166,25 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
#ifdef CONFIG_TMPFS_POSIX_ACL
sb->s_flags |= MS_POSIXACL;
#endif
+ sbinfo->s_kobj.kset = shmem_kset;
+ init_completion(&sbinfo->s_kobj_unregister);
+ err = kobject_init_and_add(&sbinfo->s_kobj, &shmem_ktype, NULL,
+ "%s-%u", sb->s_id, no++);
+ if (err)
+ goto failed;
inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
if (!inode)
- goto failed;
+ goto failed_kobj;
inode->i_uid = sbinfo->uid;
inode->i_gid = sbinfo->gid;
sb->s_root = d_make_root(inode);
if (!sb->s_root)
- goto failed;
+ goto failed_kobj;
return 0;
+failed_kobj:
+ kobject_del(&sbinfo->s_kobj);
failed:
shmem_put_super(sb);
return err;
@@ -3225,6 +3354,10 @@ int __init shmem_init(void)
if (shmem_inode_cachep)
return 0;
+ shmem_kset = kset_create_and_add("tmpfs", NULL, fs_kobj);
+ if (!shmem_kset)
+ return -ENOMEM;
+
error = bdi_init(&shmem_backing_dev_info);
if (error)
goto out4;
@@ -3255,6 +3388,7 @@ out3:
bdi_destroy(&shmem_backing_dev_info);
out4:
shm_mnt = ERR_PTR(error);
+ kset_unregister(shmem_kset);
return error;
}
--
1.9.1
--
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