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Btrfs: fix unprotected device's variants on 32bits machine

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->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>
This commit is contained in:
Miao Xie
2014-09-03 21:35:38 +08:00
committed by Chris Mason
parent 1c1161870c
commit 7cc8e58d53
4 changed files with 124 additions and 29 deletions
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84
fs/btrfs/volumes.h
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@@ -32,6 +32,19 @@ struct btrfs_pending_bios {
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 @@ struct btrfs_device {
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 @@ struct btrfs_device {
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 */