Unverified Commit 7f9bfafc authored by Christian Brauner's avatar Christian Brauner
Browse files

fs: use xarray for old mount id 

While the ida does use the xarray internally we can use it explicitly
which allows us to increment the unique mount id under the xa lock.
This allows us to remove the atomic as we're now allocating both ids in
one go.

Link: https://lore.kernel.org/r/20241217-erhielten-regung-44bb1604ca8f@brauner


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 87fc11ae

fs/namespace.c

+10 −9
Original line number Diff line number Diff line
@@ -65,12 +65,12 @@ static int __init set_mphash_entries(char *str) 
__setup("mphash_entries=", set_mphash_entries);



static u64 event;

static DEFINE_IDA(mnt_id_ida);

static DEFINE_XARRAY_FLAGS(mnt_id_xa, XA_FLAGS_ALLOC);

static DEFINE_IDA(mnt_group_ida);



/* Don't allow confusion with old 32bit mount ID */

#define MNT_UNIQUE_ID_OFFSET (1ULL << 31)

static atomic64_t mnt_id_ctr = ATOMIC64_INIT(MNT_UNIQUE_ID_OFFSET);

static u64 mnt_id_ctr = MNT_UNIQUE_ID_OFFSET;



static struct hlist_head *mount_hashtable __ro_after_init;

static struct hlist_head *mountpoint_hashtable __ro_after_init;
@@ -267,18 +267,19 @@ static inline struct hlist_head *mp_hash(struct dentry *dentry) 


static int mnt_alloc_id(struct mount *mnt)

{

	int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);

	int res;



	if (res < 0)

	xa_lock(&mnt_id_xa);

	res = __xa_alloc(&mnt_id_xa, &mnt->mnt_id, mnt, XA_LIMIT(1, INT_MAX), GFP_KERNEL);

	if (!res)

		mnt->mnt_id_unique = ++mnt_id_ctr;

	xa_unlock(&mnt_id_xa);

	return res;

	mnt->mnt_id = res;

	mnt->mnt_id_unique = atomic64_inc_return(&mnt_id_ctr);

	return 0;

}



static void mnt_free_id(struct mount *mnt)

{

	ida_free(&mnt_id_ida, mnt->mnt_id);

	xa_erase(&mnt_id_xa, mnt->mnt_id);

}



/*