From 9504e0864b58b4a304820dcf3755f1da80d5e72f Mon Sep 17 00:00:00 2001 From: "Martin K. Petersen" Date: Mon, 21 Dec 2009 15:55:51 +0100 Subject: block: Fix topology stacking for data and discard alignment The stacking code incorrectly scaled up the data offset in some cases causing misaligned devices to report alignment. Rewrite the stacking algorithm to remedy this and apply the same alignment principles to the discard handling. Signed-off-by: Martin K. Petersen Signed-off-by: Jens Axboe --- block/blk-settings.c | 87 ++++++++++++++++++++++++++++++---------------------- 1 file changed, 50 insertions(+), 37 deletions(-) (limited to 'block/blk-settings.c') diff --git a/block/blk-settings.c b/block/blk-settings.c index 6ae118d6e193..e14fcbcedbfa 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -517,9 +517,8 @@ static unsigned int lcm(unsigned int a, unsigned int b) int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, sector_t offset) { - int ret; - - ret = 0; + sector_t alignment; + unsigned int top, bottom, granularity; t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); @@ -537,6 +536,19 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->max_segment_size = min_not_zero(t->max_segment_size, b->max_segment_size); + granularity = max(b->physical_block_size, b->io_min); + alignment = b->alignment_offset - (offset & (granularity - 1)); + + if (t->alignment_offset != alignment) { + + top = max(t->physical_block_size, t->io_min) + + t->alignment_offset; + bottom = granularity + alignment; + + if (max(top, bottom) & (min(top, bottom) - 1)) + t->misaligned = 1; + } + t->logical_block_size = max(t->logical_block_size, b->logical_block_size); @@ -544,54 +556,55 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, b->physical_block_size); t->io_min = max(t->io_min, b->io_min); + t->io_opt = lcm(t->io_opt, b->io_opt); + t->no_cluster |= b->no_cluster; t->discard_zeroes_data &= b->discard_zeroes_data; - /* Bottom device offset aligned? */ - if (offset && - (offset & (b->physical_block_size - 1)) != b->alignment_offset) { + if (t->physical_block_size & (t->logical_block_size - 1)) { + t->physical_block_size = t->logical_block_size; t->misaligned = 1; - ret = -1; } - /* - * Temporarily disable discard granularity. It's currently buggy - * since we default to 0 for discard_granularity, hence this - * "failure" will always trigger for non-zero offsets. - */ -#if 0 - if (offset && - (offset & (b->discard_granularity - 1)) != b->discard_alignment) { - t->discard_misaligned = 1; - ret = -1; + if (t->io_min & (t->physical_block_size - 1)) { + t->io_min = t->physical_block_size; + t->misaligned = 1; } -#endif - /* If top has no alignment offset, inherit from bottom */ - if (!t->alignment_offset) - t->alignment_offset = - b->alignment_offset & (b->physical_block_size - 1); + if (t->io_opt & (t->physical_block_size - 1)) { + t->io_opt = 0; + t->misaligned = 1; + } - if (!t->discard_alignment) - t->discard_alignment = - b->discard_alignment & (b->discard_granularity - 1); + t->alignment_offset = lcm(t->alignment_offset, alignment) + & (max(t->physical_block_size, t->io_min) - 1); - /* Top device aligned on logical block boundary? */ - if (t->alignment_offset & (t->logical_block_size - 1)) { + if (t->alignment_offset & (t->logical_block_size - 1)) t->misaligned = 1; - ret = -1; - } - /* Find lcm() of optimal I/O size and granularity */ - t->io_opt = lcm(t->io_opt, b->io_opt); - t->discard_granularity = lcm(t->discard_granularity, - b->discard_granularity); + /* Discard alignment and granularity */ + if (b->discard_granularity) { + + alignment = b->discard_alignment - + (offset & (b->discard_granularity - 1)); + + if (t->discard_granularity != 0 && + t->discard_alignment != alignment) { + top = t->discard_granularity + t->discard_alignment; + bottom = b->discard_granularity + alignment; - /* Verify that optimal I/O size is a multiple of io_min */ - if (t->io_min && t->io_opt % t->io_min) - ret = -1; + /* Verify that top and bottom intervals line up */ + if (max(top, bottom) & (min(top, bottom) - 1)) + t->discard_misaligned = 1; + } + + t->discard_granularity = max(t->discard_granularity, + b->discard_granularity); + t->discard_alignment = lcm(t->discard_alignment, alignment) & + (t->discard_granularity - 1); + } - return ret; + return t->misaligned ? -1 : 0; } EXPORT_SYMBOL(blk_stack_limits); -- cgit v1.2.3 From 81744ee44ab2845c16ffd7d6f762f7b4a49a4750 Mon Sep 17 00:00:00 2001 From: "Martin K. Petersen" Date: Tue, 29 Dec 2009 08:35:35 +0100 Subject: block: Fix incorrect alignment offset reporting and update documentation queue_sector_alignment_offset returned the wrong value which caused partitions to report an incorrect alignment_offset. Since offset alignment calculation is needed several places it has been split into a separate helper function. The topology stacking function has been updated accordingly. Furthermore, comments have been added to clarify how the stacking function works. Signed-off-by: Martin K. Petersen Tested-by: Mike Snitzer Signed-off-by: Jens Axboe --- block/blk-settings.c | 44 +++++++++++++++++++++++++++++++++----------- include/linux/blkdev.h | 11 +++++++++-- 2 files changed, 42 insertions(+), 13 deletions(-) (limited to 'block/blk-settings.c') diff --git a/block/blk-settings.c b/block/blk-settings.c index e14fcbcedbfa..d52d4adc440b 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -505,20 +505,30 @@ static unsigned int lcm(unsigned int a, unsigned int b) /** * blk_stack_limits - adjust queue_limits for stacked devices - * @t: the stacking driver limits (top) - * @b: the underlying queue limits (bottom) + * @t: the stacking driver limits (top device) + * @b: the underlying queue limits (bottom, component device) * @offset: offset to beginning of data within component device * * Description: - * Merges two queue_limit structs. Returns 0 if alignment didn't - * change. Returns -1 if adding the bottom device caused - * misalignment. + * This function is used by stacking drivers like MD and DM to ensure + * that all component devices have compatible block sizes and + * alignments. The stacking driver must provide a queue_limits + * struct (top) and then iteratively call the stacking function for + * all component (bottom) devices. The stacking function will + * attempt to combine the values and ensure proper alignment. + * + * Returns 0 if the top and bottom queue_limits are compatible. The + * top device's block sizes and alignment offsets may be adjusted to + * ensure alignment with the bottom device. If no compatible sizes + * and alignments exist, -1 is returned and the resulting top + * queue_limits will have the misaligned flag set to indicate that + * the alignment_offset is undefined. */ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, sector_t offset) { sector_t alignment; - unsigned int top, bottom, granularity; + unsigned int top, bottom; t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); @@ -536,15 +546,18 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->max_segment_size = min_not_zero(t->max_segment_size, b->max_segment_size); - granularity = max(b->physical_block_size, b->io_min); - alignment = b->alignment_offset - (offset & (granularity - 1)); + alignment = queue_limit_alignment_offset(b, offset); + /* Bottom device has different alignment. Check that it is + * compatible with the current top alignment. + */ if (t->alignment_offset != alignment) { top = max(t->physical_block_size, t->io_min) + t->alignment_offset; - bottom = granularity + alignment; + bottom = max(b->physical_block_size, b->io_min) + alignment; + /* Verify that top and bottom intervals line up */ if (max(top, bottom) & (min(top, bottom) - 1)) t->misaligned = 1; } @@ -561,32 +574,39 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->no_cluster |= b->no_cluster; t->discard_zeroes_data &= b->discard_zeroes_data; + /* Physical block size a multiple of the logical block size? */ if (t->physical_block_size & (t->logical_block_size - 1)) { t->physical_block_size = t->logical_block_size; t->misaligned = 1; } + /* Minimum I/O a multiple of the physical block size? */ if (t->io_min & (t->physical_block_size - 1)) { t->io_min = t->physical_block_size; t->misaligned = 1; } + /* Optimal I/O a multiple of the physical block size? */ if (t->io_opt & (t->physical_block_size - 1)) { t->io_opt = 0; t->misaligned = 1; } + /* Find lowest common alignment_offset */ t->alignment_offset = lcm(t->alignment_offset, alignment) & (max(t->physical_block_size, t->io_min) - 1); + /* Verify that new alignment_offset is on a logical block boundary */ if (t->alignment_offset & (t->logical_block_size - 1)) t->misaligned = 1; /* Discard alignment and granularity */ if (b->discard_granularity) { + unsigned int granularity = b->discard_granularity; + offset &= granularity - 1; - alignment = b->discard_alignment - - (offset & (b->discard_granularity - 1)); + alignment = (granularity + b->discard_alignment - offset) + & (granularity - 1); if (t->discard_granularity != 0 && t->discard_alignment != alignment) { @@ -598,6 +618,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->discard_misaligned = 1; } + t->max_discard_sectors = min_not_zero(t->max_discard_sectors, + b->max_discard_sectors); t->discard_granularity = max(t->discard_granularity, b->discard_granularity); t->discard_alignment = lcm(t->discard_alignment, alignment) & diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 784a919aa0d0..59b832be3044 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1116,11 +1116,18 @@ static inline int queue_alignment_offset(struct request_queue *q) return q->limits.alignment_offset; } +static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t offset) +{ + unsigned int granularity = max(lim->physical_block_size, lim->io_min); + + offset &= granularity - 1; + return (granularity + lim->alignment_offset - offset) & (granularity - 1); +} + static inline int queue_sector_alignment_offset(struct request_queue *q, sector_t sector) { - return ((sector << 9) - q->limits.alignment_offset) - & (q->limits.io_min - 1); + return queue_limit_alignment_offset(&q->limits, sector << 9); } static inline int bdev_alignment_offset(struct block_device *bdev) -- cgit v1.2.3