[Devel] [PATCH RH7] ipc: add export_operations to mqueue sb
Konstantin Khorenko
khorenko at virtuozzo.com
Thu Sep 24 13:38:24 MSK 2020
On 09/09/2020 01:19 PM, Pavel Tikhomirov wrote:
> Looks good.
>
> Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>
> But please also see two non-critical questions below.
Andrey, any answer on that?
> On 9/8/20 5:33 PM, Andrey Zhadchenko wrote:
>> criu uses fhandle from fdinfo to dump inotify objects, but mqueue has no
>> export_operations in super block. However, they are needed if we want to
>> operate with files using fhandles.
>> Add hash table as a storage for exported inodes.
>>
>> https://jira.sw.ru/browse/PSBM-103727
>> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
>> ---
>> ipc/mqueue.c | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 150 insertions(+)
>>
>> diff --git a/ipc/mqueue.c b/ipc/mqueue.c
>> index 458e655..48ec6f8 100644
>> --- a/ipc/mqueue.c
>> +++ b/ipc/mqueue.c
>> @@ -35,6 +35,8 @@
>> #include <linux/ipc_namespace.h>
>> #include <linux/user_namespace.h>
>> #include <linux/slab.h>
>> +#include <linux/exportfs.h>
>> +#include <linux/random.h>
>>
>> #include <net/sock.h>
>> #include "util.h"
>> @@ -86,6 +88,7 @@ struct mqueue_inode_info {
>> };
>>
>> static const struct inode_operations mqueue_dir_inode_operations;
>> +static const struct export_operations mqueue_export_ops;
>> static const struct file_operations mqueue_file_operations;
>> static const struct super_operations mqueue_super_ops;
>> static void remove_notification(struct mqueue_inode_info *info);
>> @@ -117,6 +120,144 @@ static struct ipc_namespace *get_ns_from_inode(struct inode *inode)
>> return ns;
>> }
>>
>> +/*
>> + * hashtable for inodes that have exported fhandles.
>> + * When we export fhandle, we add it's inode into
>> + * hashtable so we can find it fast
>> + */
>> +
>> +#define MQUEUE_INODE_HASH_BITS 7
>
> Why you've chosen smaller hash size than for cgroups?
> #define CGROUP_INODE_HASH_BITS 10
>
>> +static DEFINE_HASHTABLE(mqueue_inode_table, MQUEUE_INODE_HASH_BITS);
>> +static DEFINE_SPINLOCK(mqueue_inode_table_lock);
>> +
>> +struct mq_inode_hitem {
>> + struct inode *inode;
>> + struct hlist_node hlist;
>> +};
>> +
>> +static inline unsigned long mqueue_inode_get_hash(unsigned int i_ino)
>> +{
>> + return hash_32(i_ino, MQUEUE_INODE_HASH_BITS);
>> +}
>> +
>> +static struct mq_inode_hitem *mqueue_find_item_no_lock(unsigned long fh[2])
>> +{
>> + struct mq_inode_hitem *i;
>> + struct hlist_head *head = mqueue_inode_table
>> + + mqueue_inode_get_hash(fh[1]);
>> + struct mq_inode_hitem *found = NULL;
>> +
>> + hlist_for_each_entry(i, head, hlist) {
>> + if (i->inode->i_generation == fh[0] &&
>> + i->inode->i_ino == fh[1]) {
>> + found = i;
>> + break;
>> + }
>> + }
>> +
>> + return found;
>> +}
>> +
>> +static struct inode *mqueue_find_inode(unsigned long fh[2], char take_ref)
>> +{
>> + struct mq_inode_hitem *item;
>> + struct inode *ret = NULL;
>> +
>> + spin_lock(&mqueue_inode_table_lock);
>> + item = mqueue_find_item_no_lock(fh);
>> + if (item && take_ref && !igrab(item->inode))
>> + item = NULL;
>> + spin_unlock(&mqueue_inode_table_lock);
>> +
>> + if (item)
>> + ret = item->inode;
>> +
>> + return ret;
>> +}
>> +
>> +static int mqueue_hash_add(struct inode *inode)
>> +{
>> + unsigned long fh[2] = {inode->i_generation, inode->i_ino};
>> +
>> + if (!mqueue_find_inode(fh, 0)) {
>> + struct mq_inode_hitem *item;
>> + struct mq_inode_hitem *existing_item = 0;
>> + struct hlist_head *head = mqueue_inode_table
>> + + mqueue_inode_get_hash(inode->i_ino);
>> +
>> + item = kmalloc(sizeof(struct mq_inode_hitem), GFP_KERNEL);
>> + if (!item)
>> + return -ENOMEM;
>> + item->inode = inode;
>> +
>> + spin_lock(&mqueue_inode_table_lock);
>> + existing_item = mqueue_find_item_no_lock(fh);
>> + if (!existing_item)
>> + hlist_add_head(&item->hlist, head);
>> + spin_unlock(&mqueue_inode_table_lock);
>> +
>> + if (existing_item)
>> + kfree(item);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void mqueue_hash_del(struct inode *inode)
>> +{
>> + struct mq_inode_hitem *item;
>> + unsigned long fh[2] = {inode->i_generation, inode->i_ino};
>> +
>> + spin_lock(&mqueue_inode_table_lock);
>> + item = mqueue_find_item_no_lock(fh);
>> + if (item)
>> + hlist_del(&item->hlist);
>> + spin_unlock(&mqueue_inode_table_lock);
>> +
>> + kfree(item);
>> + return;
>> +}
>> +
>> +static struct dentry *mqueue_fh_to_dentry(struct super_block *sb,
>> + struct fid *fid, int fh_len, int fh_type)
>> +{
>> + struct inode *inode;
>> + struct dentry *dentry = ERR_PTR(-ENOENT);
>> + unsigned long fhandle[2] = {fid->raw[0], fid->raw[1]};
>> +
>> + if (fh_len < 2)
>> + return NULL;
>> +
>> + inode = mqueue_find_inode(fhandle, 1);
>> + if (inode) {
>> + dentry = d_find_alias(inode);
>> + iput(inode);
>> + }
>> + return dentry;
>> +}
>> +
>> +static int mqueue_encode_fh(struct inode *inode, __u32 *fh, int *len,
>> + struct inode *parent)
>> +{
>> + if (*len < 2) {
>> + *len = 2;
>> + return FILEID_INVALID;
>> + }
>> +
>> + /*
>> + * encode_fh is expected to return 255 (FILEID_INVALID)
>> + * in case of failure. We can't return ENOMEM, so
>> + * return FILEID_INVALID at least.
>> + */
>> + if (mqueue_hash_add(inode))
>> + return FILEID_INVALID;
>> +
>> + fh[0] = inode->i_generation;
>> + fh[1] = inode->i_ino;
>> + *len = 2;
>> + return 1;
>> +}
>> +
>> /* Auxiliary functions to manipulate messages' list */
>> static int msg_insert(struct msg_msg *msg, struct mqueue_inode_info *info)
>> {
>> @@ -226,6 +367,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
>> goto err;
>>
>> inode->i_ino = get_next_ino();
>> + inode->i_generation = prandom_u32();
>> inode->i_mode = mode;
>> inode->i_uid = current_fsuid();
>> inode->i_gid = current_fsgid();
>> @@ -316,6 +458,7 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
>> sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
>> sb->s_magic = MQUEUE_MAGIC;
>> sb->s_op = &mqueue_super_ops;
>> + sb->s_export_op = &mqueue_export_ops;
>>
>> inode = mqueue_get_inode(sb, ns, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
>> if (IS_ERR(inode))
>> @@ -382,6 +525,8 @@ static void mqueue_evict_inode(struct inode *inode)
>> if (S_ISDIR(inode->i_mode))
>> return;
>>
>> + mqueue_hash_del(inode);
>> +
>
> Looks like for cgroups we should've also put cgroup_hash_del to
> ->evict_inode helper, to be able to use igrab in cgroup_find_inode.
> Shouldn't we?
>
>> ipc_ns = get_ns_from_inode(inode);
>> info = MQUEUE_I(inode);
>> spin_lock(&info->lock);
>> @@ -1376,6 +1521,11 @@ static const struct inode_operations mqueue_dir_inode_operations = {
>> .unlink = mqueue_unlink,
>> };
>>
>> +static const struct export_operations mqueue_export_ops = {
>> + .encode_fh = mqueue_encode_fh,
>> + .fh_to_dentry = mqueue_fh_to_dentry,
>> +};
>> +
>> static const struct file_operations mqueue_file_operations = {
>> .flush = mqueue_flush_file,
>> .poll = mqueue_poll_file,
>>
>
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