Btrfs: fix unprotected device's variants on 32bits machine
->total_bytes,->disk_total_bytes,->bytes_used is protected by chunk
lock when we change them, but sometimes we read them without any lock,
and we might get unexpected value. We fix this problem like inode's
i_size.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index f79d532..76600a3 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -32,6 +32,19 @@
struct bio *tail;
};
+/*
+ * Use sequence counter to get consistent device stat data on
+ * 32-bit processors.
+ */
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+#include <linux/seqlock.h>
+#define __BTRFS_NEED_DEVICE_DATA_ORDERED
+#define btrfs_device_data_ordered_init(device) \
+ seqcount_init(&device->data_seqcount)
+#else
+#define btrfs_device_data_ordered_init(device) do { } while (0)
+#endif
+
struct btrfs_device {
struct list_head dev_list;
struct list_head dev_alloc_list;
@@ -61,6 +74,10 @@
int can_discard;
int is_tgtdev_for_dev_replace;
+#ifdef __BTRFS_NEED_DEVICE_DATA_ORDERED
+ seqcount_t data_seqcount;
+#endif
+
/* the internal btrfs device id */
u64 devid;
@@ -133,6 +150,73 @@
atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
};
+/*
+ * If we read those variants at the context of their own lock, we needn't
+ * use the following helpers, reading them directly is safe.
+ */
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+#define BTRFS_DEVICE_GETSET_FUNCS(name) \
+static inline u64 \
+btrfs_device_get_##name(const struct btrfs_device *dev) \
+{ \
+ u64 size; \
+ unsigned int seq; \
+ \
+ do { \
+ seq = read_seqcount_begin(&dev->data_seqcount); \
+ size = dev->name; \
+ } while (read_seqcount_retry(&dev->data_seqcount, seq)); \
+ return size; \
+} \
+ \
+static inline void \
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size) \
+{ \
+ preempt_disable(); \
+ write_seqcount_begin(&dev->data_seqcount); \
+ dev->name = size; \
+ write_seqcount_end(&dev->data_seqcount); \
+ preempt_enable(); \
+}
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
+#define BTRFS_DEVICE_GETSET_FUNCS(name) \
+static inline u64 \
+btrfs_device_get_##name(const struct btrfs_device *dev) \
+{ \
+ u64 size; \
+ \
+ preempt_disable(); \
+ size = dev->name; \
+ preempt_enable(); \
+ return size; \
+} \
+ \
+static inline void \
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size) \
+{ \
+ preempt_disable(); \
+ dev->name = size; \
+ preempt_enable(); \
+}
+#else
+#define BTRFS_DEVICE_GETSET_FUNCS(name) \
+static inline u64 \
+btrfs_device_get_##name(const struct btrfs_device *dev) \
+{ \
+ return dev->name; \
+} \
+ \
+static inline void \
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size) \
+{ \
+ dev->name = size; \
+}
+#endif
+
+BTRFS_DEVICE_GETSET_FUNCS(total_bytes);
+BTRFS_DEVICE_GETSET_FUNCS(disk_total_bytes);
+BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
+
struct btrfs_fs_devices {
u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */