Add a function to find the max alignment of an atomic write for a bdev
when provided with an offset and length.
We should be able to optimise this function later, most especially since
the values involved are powers-of-2.
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
block/bdev.c | 39 +++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 9 +++++++++
2 files changed, 48 insertions(+)
diff --git a/block/bdev.c b/block/bdev.c
index 6a5fd5abaadc..3373f0d5cad9 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -46,6 +46,45 @@ struct block_device *I_BDEV(struct inode *inode)
}
EXPORT_SYMBOL(I_BDEV);
+unsigned int bdev_find_max_atomic_write_alignment(struct block_device *bdev,
+ loff_t pos, unsigned int len)
+{
+ struct request_queue *bd_queue = bdev->bd_queue;
+ struct queue_limits *limits = &bd_queue->limits;
+ unsigned int atomic_write_unit_min = limits->atomic_write_unit_min;
+ unsigned int atomic_write_unit_max = limits->atomic_write_unit_max;
+ unsigned int max_align;
+
+ pos /= SECTOR_SIZE;
+ len /= SECTOR_SIZE;
+
+ max_align = min_not_zero(len, atomic_write_unit_max);
+
+ if (len <= 1)
+ return atomic_write_unit_min * SECTOR_SIZE;
+
+ max_align = rounddown_pow_of_two(max_align);
+ while (1) {
+ unsigned int mod1, mod2;
+
+ if (max_align == 0)
+ return atomic_write_unit_min * SECTOR_SIZE;
+
+ /* This should not happen */
+ if (!is_power_of_2(max_align))
+ goto end;
+
+ mod1 = len % max_align;
+ mod2 = pos % max_align;
+ if (!mod1 && !mod2)
+ break;
+end:
+ max_align /= 2;
+ }
+
+ return max_align * SECTOR_SIZE;
+}
+
static void bdev_write_inode(struct block_device *bdev)
{
struct inode *inode = bdev->bd_inode;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 19d33b2897b2..96138550928c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1529,6 +1529,8 @@ void sync_bdevs(bool wait);
void bdev_statx_dioalign(struct inode *inode, struct kstat *stat);
void bdev_statx_atomic(struct inode *inode, struct kstat *stat);
void printk_all_partitions(void);
+unsigned int bdev_find_max_atomic_write_alignment(struct block_device *bdev,
+ loff_t pos, unsigned int len);
#else
static inline void invalidate_bdev(struct block_device *bdev)
{
@@ -1553,6 +1555,13 @@ static inline void bdev_statx_atomic(struct inode *inode, struct kstat *stat)
static inline void printk_all_partitions(void)
{
}
+static inline unsigned int bdev_find_max_atomic_write_alignment(
+ struct block_device *bdev,
+ loff_t pos, unsigned int len)
+{
+ return 0;
+}
+
#endif /* CONFIG_BLOCK */
int fsync_bdev(struct block_device *bdev);
--
2.31.1
