// SPDX-License-Identifier: GPL-2.0 /* * Functions related to setting various queue properties from drivers */ #include #include #include #include #include #include /* for max_pfn/max_low_pfn */ #include #include #include #include #include #include "blk.h" #include "blk-wbt.h" unsigned long blk_max_low_pfn; EXPORT_SYMBOL(blk_max_low_pfn); unsigned long blk_max_pfn; void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout) { q->rq_timeout = timeout; } EXPORT_SYMBOL_GPL(blk_queue_rq_timeout); /** * blk_set_default_limits - reset limits to default values * @lim: the queue_limits structure to reset * * Description: * Returns a queue_limit struct to its default state. */ void blk_set_default_limits(struct queue_limits *lim) { lim->max_segments = BLK_MAX_SEGMENTS; lim->max_discard_segments = 1; lim->max_integrity_segments = 0; lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK; lim->virt_boundary_mask = 0; lim->max_segment_size = BLK_MAX_SEGMENT_SIZE; lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS; lim->max_dev_sectors = 0; lim->chunk_sectors = 0; lim->max_write_same_sectors = 0; lim->max_write_zeroes_sectors = 0; lim->max_zone_append_sectors = 0; lim->max_discard_sectors = 0; lim->max_hw_discard_sectors = 0; lim->discard_granularity = 0; lim->discard_alignment = 0; lim->discard_misaligned = 0; lim->logical_block_size = lim->physical_block_size = lim->io_min = 512; lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT); lim->alignment_offset = 0; lim->io_opt = 0; lim->misaligned = 0; lim->zoned = BLK_ZONED_NONE; } EXPORT_SYMBOL(blk_set_default_limits); /** * blk_set_stacking_limits - set default limits for stacking devices * @lim: the queue_limits structure to reset * * Description: * Returns a queue_limit struct to its default state. Should be used * by stacking drivers like DM that have no internal limits. */ void blk_set_stacking_limits(struct queue_limits *lim) { blk_set_default_limits(lim); /* Inherit limits from component devices */ lim->max_segments = USHRT_MAX; lim->max_discard_segments = USHRT_MAX; lim->max_hw_sectors = UINT_MAX; lim->max_segment_size = UINT_MAX; lim->max_sectors = UINT_MAX; lim->max_dev_sectors = UINT_MAX; lim->max_write_same_sectors = UINT_MAX; lim->max_write_zeroes_sectors = UINT_MAX; lim->max_zone_append_sectors = UINT_MAX; } EXPORT_SYMBOL(blk_set_stacking_limits); /** * blk_queue_bounce_limit - set bounce buffer limit for queue * @q: the request queue for the device * @max_addr: the maximum address the device can handle * * Description: * Different hardware can have different requirements as to what pages * it can do I/O directly to. A low level driver can call * blk_queue_bounce_limit to have lower memory pages allocated as bounce * buffers for doing I/O to pages residing above @max_addr. **/ void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr) { unsigned long b_pfn = max_addr >> PAGE_SHIFT; int dma = 0; q->bounce_gfp = GFP_NOIO; #if BITS_PER_LONG == 64 /* * Assume anything <= 4GB can be handled by IOMMU. Actually * some IOMMUs can handle everything, but I don't know of a * way to test this here. */ if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) dma = 1; q->limits.bounce_pfn = max(max_low_pfn, b_pfn); #else if (b_pfn < blk_max_low_pfn) dma = 1; q->limits.bounce_pfn = b_pfn; #endif if (dma) { init_emergency_isa_pool(); q->bounce_gfp = GFP_NOIO | GFP_DMA; q->limits.bounce_pfn = b_pfn; } } EXPORT_SYMBOL(blk_queue_bounce_limit); /** * blk_queue_max_hw_sectors - set max sectors for a request for this queue * @q: the request queue for the device * @max_hw_sectors: max hardware sectors in the usual 512b unit * * Description: * Enables a low level driver to set a hard upper limit, * max_hw_sectors, on the size of requests. max_hw_sectors is set by * the device driver based upon the capabilities of the I/O * controller. * * max_dev_sectors is a hard limit imposed by the storage device for * READ/WRITE requests. It is set by the disk driver. * * max_sectors is a soft limit imposed by the block layer for * filesystem type requests. This value can be overridden on a * per-device basis in /sys/block//queue/max_sectors_kb. * The soft limit can not exceed max_hw_sectors. **/ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors) { struct queue_limits *limits = &q->limits; unsigned int max_sectors; if ((max_hw_sectors << 9) < PAGE_SIZE) { max_hw_sectors = 1 << (PAGE_SHIFT - 9); printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_hw_sectors); } limits->max_hw_sectors = max_hw_sectors; max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors); max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS); limits->max_sectors = max_sectors; q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9); } EXPORT_SYMBOL(blk_queue_max_hw_sectors); /** * blk_queue_chunk_sectors - set size of the chunk for this queue * @q: the request queue for the device * @chunk_sectors: chunk sectors in the usual 512b unit * * Description: * If a driver doesn't want IOs to cross a given chunk size, it can set * this limit and prevent merging across chunks. Note that the chunk size * must currently be a power-of-2 in sectors. Also note that the block * layer must accept a page worth of data at any offset. So if the * crossing of chunks is a hard limitation in the driver, it must still be * prepared to split single page bios. **/ void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors) { BUG_ON(!is_power_of_2(chunk_sectors)); q->limits.chunk_sectors = chunk_sectors; } EXPORT_SYMBOL(blk_queue_chunk_sectors); /** * blk_queue_max_discard_sectors - set max sectors for a single discard * @q: the request queue for the device * @max_discard_sectors: maximum number of sectors to discard **/ void blk_queue_max_discard_sectors(struct request_queue *q, unsigned int max_discard_sectors) { q->limits.max_hw_discard_sectors = max_discard_sectors; q->limits.max_discard_sectors = max_discard_sectors; } EXPORT_SYMBOL(blk_queue_max_discard_sectors); /** * blk_queue_max_write_same_sectors - set max sectors for a single write same * @q: the request queue for the device * @max_write_same_sectors: maximum number of sectors to write per command **/ void blk_queue_max_write_same_sectors(struct request_queue *q, unsigned int max_write_same_sectors) { q->limits.max_write_same_sectors = max_write_same_sectors; } EXPORT_SYMBOL(blk_queue_max_write_same_sectors); /** * blk_queue_max_write_zeroes_sectors - set max sectors for a single * write zeroes * @q: the request queue for the device * @max_write_zeroes_sectors: maximum number of sectors to write per command **/ void blk_queue_max_write_zeroes_sectors(struct request_queue *q, unsigned int max_write_zeroes_sectors) { q->limits.max_write_zeroes_sectors = max_write_zeroes_sectors; } EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors); /** * blk_queue_max_zone_append_sectors - set max sectors for a single zone append * @q: the request queue for the device * @max_zone_append_sectors: maximum number of sectors to write per command **/ void blk_queue_max_zone_append_sectors(struct request_queue *q, unsigned int max_zone_append_sectors) { unsigned int max_sectors; if (WARN_ON(!blk_queue_is_zoned(q))) return; max_sectors = min(q->limits.max_hw_sectors, max_zone_append_sectors); max_sectors = min(q->limits.chunk_sectors, max_sectors); /* * Signal eventual driver bugs resulting in the max_zone_append sectors limit * being 0 due to a 0 argument, the chunk_sectors limit (zone size) not set, * or the max_hw_sectors limit not set. */ WARN_ON(!max_sectors); q->limits.max_zone_append_sectors = max_sectors; } EXPORT_SYMBOL_GPL(blk_queue_max_zone_append_sectors); /** * blk_queue_max_segments - set max hw segments for a request for this queue * @q: the request queue for the device * @max_segments: max number of segments * * Description: * Enables a low level driver to set an upper limit on the number of * hw data segments in a request. **/ void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments) { if (!max_segments) { max_segments = 1; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_segments); } q->limits.max_segments = max_segments; } EXPORT_SYMBOL(blk_queue_max_segments); /** * blk_queue_max_discard_segments - set max segments for discard requests * @q: the request queue for the device * @max_segments: max number of segments * * Description: * Enables a low level driver to set an upper limit on the number of * segments in a discard request. **/ void blk_queue_max_discard_segments(struct request_queue *q, unsigned short max_segments) { q->limits.max_discard_segments = max_segments; } EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments); /** * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg * @q: the request queue for the device * @max_size: max size of segment in bytes * * Description: * Enables a low level driver to set an upper limit on the size of a * coalesced segment **/ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) { if (max_size < PAGE_SIZE) { max_size = PAGE_SIZE; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_size); } /* see blk_queue_virt_boundary() for the explanation */ WARN_ON_ONCE(q->limits.virt_boundary_mask); q->limits.max_segment_size = max_size; } EXPORT_SYMBOL(blk_queue_max_segment_size); /** * blk_queue_logical_block_size - set logical block size for the queue * @q: the request queue for the device * @size: the logical block size, in bytes * * Description: * This should be set to the lowest possible block size that the * storage device can address. The default of 512 covers most * hardware. **/ void blk_queue_logical_block_size(struct request_queue *q, unsigned int size) { q->limits.logical_block_size = size; if (q->limits.physical_block_size < size) q->limits.physical_block_size = size; if (q->limits.io_min < q->limits.physical_block_size) q->limits.io_min = q->limits.physical_block_size; } EXPORT_SYMBOL(blk_queue_logical_block_size); /** * blk_queue_physical_block_size - set physical block size for the queue * @q: the request queue for the device * @size: the physical block size, in bytes * * Description: * This should be set to the lowest possible sector size that the * hardware can operate on without reverting to read-modify-write * operations. */ void blk_queue_physical_block_size(struct request_queue *q, unsigned int size) { q->limits.physical_block_size = size; if (q->limits.physical_block_size < q->limits.logical_block_size) q->limits.physical_block_size = q->limits.logical_block_size; if (q->limits.io_min < q->limits.physical_block_size) q->limits.io_min = q->limits.physical_block_size; } EXPORT_SYMBOL(blk_queue_physical_block_size); /** * blk_queue_alignment_offset - set physical block alignment offset * @q: the request queue for the device * @offset: alignment offset in bytes * * Description: * Some devices are naturally misaligned to compensate for things like * the legacy DOS partition table 63-sector offset. Low-level drivers * should call this function for devices whose first sector is not * naturally aligned. */ void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset) { q->limits.alignment_offset = offset & (q->limits.physical_block_size - 1); q->limits.misaligned = 0; } EXPORT_SYMBOL(blk_queue_alignment_offset); /** * blk_limits_io_min - set minimum request size for a device * @limits: the queue limits * @min: smallest I/O size in bytes * * Description: * Some devices have an internal block size bigger than the reported * hardware sector size. This function can be used to signal the * smallest I/O the device can perform without incurring a performance * penalty. */ void blk_limits_io_min(struct queue_limits *limits, unsigned int min) { limits->io_min = min; if (limits->io_min < limits->logical_block_size) limits->io_min = limits->logical_block_size; if (limits->io_min < limits->physical_block_size) limits->io_min = limits->physical_block_size; } EXPORT_SYMBOL(blk_limits_io_min); /** * blk_queue_io_min - set minimum request size for the queue * @q: the request queue for the device * @min: smallest I/O size in bytes * * Description: * Storage devices may report a granularity or preferred minimum I/O * size which is the smallest request the device can perform without * incurring a performance penalty. For disk drives this is often the * physical block size. For RAID arrays it is often the stripe chunk * size. A properly aligned multiple of minimum_io_size is the * preferred request size for workloads where a high number of I/O * operations is desired. */ void blk_queue_io_min(struct request_queue *q, unsigned int min) { blk_limits_io_min(&q->limits, min); } EXPORT_SYMBOL(blk_queue_io_min); /** * blk_limits_io_opt - set optimal request size for a device * @limits: the queue limits * @opt: smallest I/O size in bytes * * Description: * Storage devices may report an optimal I/O size, which is the * device's preferred unit for sustained I/O. This is rarely reported * for disk drives. For RAID arrays it is usually the stripe width or * the internal track size. A properly aligned multiple of * optimal_io_size is the preferred request size for workloads where * sustained throughput is desired. */ void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt) { limits->io_opt = opt; } EXPORT_SYMBOL(blk_limits_io_opt); /** * blk_queue_io_opt - set optimal request size for the queue * @q: the request queue for the device * @opt: optimal request size in bytes * * Description: * Storage devices may report an optimal I/O size, which is the * device's preferred unit for sustained I/O. This is rarely reported * for disk drives. For RAID arrays it is usually the stripe width or * the internal track size. A properly aligned multiple of * optimal_io_size is the preferred request size for workloads where * sustained throughput is desired. */ void blk_queue_io_opt(struct request_queue *q, unsigned int opt) { blk_limits_io_opt(&q->limits, opt); } EXPORT_SYMBOL(blk_queue_io_opt); /** * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers * @t: the stacking driver (top) * @b: the underlying device (bottom) **/ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) { blk_stack_limits(&t->limits, &b->limits, 0); } EXPORT_SYMBOL(blk_queue_stack_limits); /** * blk_stack_limits - adjust queue_limits for stacked devices * @t: the stacking driver limits (top device) * @b: the underlying queue limits (bottom, component device) * @start: first data sector within component device * * Description: * 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 start) { unsigned int top, bottom, alignment, ret = 0; 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); t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors); t->max_write_same_sectors = min(t->max_write_same_sectors, b->max_write_same_sectors); t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors, b->max_write_zeroes_sectors); t->max_zone_append_sectors = min(t->max_zone_append_sectors, b->max_zone_append_sectors); t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn); t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, b->seg_boundary_mask); t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask, b->virt_boundary_mask); t->max_segments = min_not_zero(t->max_segments, b->max_segments); t->max_discard_segments = min_not_zero(t->max_discard_segments, b->max_discard_segments); t->max_integrity_segments = min_not_zero(t->max_integrity_segments, b->max_integrity_segments); t->max_segment_size = min_not_zero(t->max_segment_size, b->max_segment_size); t->misaligned |= b->misaligned; alignment = queue_limit_alignment_offset(b, start); /* 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 = max(b->physical_block_size, b->io_min) + alignment; /* Verify that top and bottom intervals line up */ if (max(top, bottom) % min(top, bottom)) { t->misaligned = 1; ret = -1; } } t->logical_block_size = max(t->logical_block_size, b->logical_block_size); t->physical_block_size = max(t->physical_block_size, b->physical_block_size); t->io_min = max(t->io_min, b->io_min); t->io_opt = lcm_not_zero(t->io_opt, b->io_opt); /* 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; ret = -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; ret = -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; ret = -1; } t->raid_partial_stripes_expensive = max(t->raid_partial_stripes_expensive, b->raid_partial_stripes_expensive); /* Find lowest common alignment_offset */ t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment) % max(t->physical_block_size, t->io_min); /* Verify that new alignment_offset is on a logical block boundary */ if (t->alignment_offset & (t->logical_block_size - 1)) { t->misaligned = 1; ret = -1; } /* Discard alignment and granularity */ if (b->discard_granularity) { alignment = queue_limit_discard_alignment(b, start); if (t->discard_granularity != 0 && t->discard_alignment != alignment) { top = t->discard_granularity + t->discard_alignment; bottom = b->discard_granularity + alignment; /* Verify that top and bottom intervals line up */ if ((max(top, bottom) % min(top, bottom)) != 0) t->discard_misaligned = 1; } t->max_discard_sectors = min_not_zero(t->max_discard_sectors, b->max_discard_sectors); t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors, b->max_hw_discard_sectors); t->discard_granularity = max(t->discard_granularity, b->discard_granularity); t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) % t->discard_granularity; } if (b->chunk_sectors) t->chunk_sectors = min_not_zero(t->chunk_sectors, b->chunk_sectors); t->zoned = max(t->zoned, b->zoned); return ret; } EXPORT_SYMBOL(blk_stack_limits); /** * disk_stack_limits - adjust queue limits for stacked drivers * @disk: MD/DM gendisk (top) * @bdev: the underlying block device (bottom) * @offset: offset to beginning of data within component device * * Description: * Merges the limits for a top level gendisk and a bottom level * block_device. */ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev, sector_t offset) { struct request_queue *t = disk->queue; if (blk_stack_limits(&t->limits, &bdev_get_queue(bdev)->limits, get_start_sect(bdev) + (offset >> 9)) < 0) { char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE]; disk_name(disk, 0, top); bdevname(bdev, bottom); printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n", top, bottom); } t->backing_dev_info->io_pages = t->limits.max_sectors >> (PAGE_SHIFT - 9); } EXPORT_SYMBOL(disk_stack_limits); /** * blk_queue_update_dma_pad - update pad mask * @q: the request queue for the device * @mask: pad mask * * Update dma pad mask. * * Appending pad buffer to a request modifies the last entry of a * scatter list such that it includes the pad buffer. **/ void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask) { if (mask > q->dma_pad_mask) q->dma_pad_mask = mask; } EXPORT_SYMBOL(blk_queue_update_dma_pad); /** * blk_queue_segment_boundary - set boundary rules for segment merging * @q: the request queue for the device * @mask: the memory boundary mask **/ void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask) { if (mask < PAGE_SIZE - 1) { mask = PAGE_SIZE - 1; printk(KERN_INFO "%s: set to minimum %lx\n", __func__, mask); } q->limits.seg_boundary_mask = mask; } EXPORT_SYMBOL(blk_queue_segment_boundary); /** * blk_queue_virt_boundary - set boundary rules for bio merging * @q: the request queue for the device * @mask: the memory boundary mask **/ void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask) { q->limits.virt_boundary_mask = mask; /* * Devices that require a virtual boundary do not support scatter/gather * I/O natively, but instead require a descriptor list entry for each * page (which might not be idential to the Linux PAGE_SIZE). Because * of that they are not limited by our notion of "segment size". */ if (mask) q->limits.max_segment_size = UINT_MAX; } EXPORT_SYMBOL(blk_queue_virt_boundary); /** * blk_queue_dma_alignment - set dma length and memory alignment * @q: the request queue for the device * @mask: alignment mask * * description: * set required memory and length alignment for direct dma transactions. * this is used when building direct io requests for the queue. * **/ void blk_queue_dma_alignment(struct request_queue *q, int mask) { q->dma_alignment = mask; } EXPORT_SYMBOL(blk_queue_dma_alignment); /** * blk_queue_update_dma_alignment - update dma length and memory alignment * @q: the request queue for the device * @mask: alignment mask * * description: * update required memory and length alignment for direct dma transactions. * If the requested alignment is larger than the current alignment, then * the current queue alignment is updated to the new value, otherwise it * is left alone. The design of this is to allow multiple objects * (driver, device, transport etc) to set their respective * alignments without having them interfere. * **/ void blk_queue_update_dma_alignment(struct request_queue *q, int mask) { BUG_ON(mask > PAGE_SIZE); if (mask > q->dma_alignment) q->dma_alignment = mask; } EXPORT_SYMBOL(blk_queue_update_dma_alignment); /** * blk_set_queue_depth - tell the block layer about the device queue depth * @q: the request queue for the device * @depth: queue depth * */ void blk_set_queue_depth(struct request_queue *q, unsigned int depth) { q->queue_depth = depth; rq_qos_queue_depth_changed(q); } EXPORT_SYMBOL(blk_set_queue_depth); /** * blk_queue_write_cache - configure queue's write cache * @q: the request queue for the device * @wc: write back cache on or off * @fua: device supports FUA writes, if true * * Tell the block layer about the write cache of @q. */ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua) { if (wc) blk_queue_flag_set(QUEUE_FLAG_WC, q); else blk_queue_flag_clear(QUEUE_FLAG_WC, q); if (fua) blk_queue_flag_set(QUEUE_FLAG_FUA, q); else blk_queue_flag_clear(QUEUE_FLAG_FUA, q); wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags)); } EXPORT_SYMBOL_GPL(blk_queue_write_cache); /** * blk_queue_required_elevator_features - Set a queue required elevator features * @q: the request queue for the target device * @features: Required elevator features OR'ed together * * Tell the block layer that for the device controlled through @q, only the * only elevators that can be used are those that implement at least the set of * features specified by @features. */ void blk_queue_required_elevator_features(struct request_queue *q, unsigned int features) { q->required_elevator_features = features; } EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features); /** * blk_queue_can_use_dma_map_merging - configure queue for merging segments. * @q: the request queue for the device * @dev: the device pointer for dma * * Tell the block layer about merging the segments by dma map of @q. */ bool blk_queue_can_use_dma_map_merging(struct request_queue *q, struct device *dev) { unsigned long boundary = dma_get_merge_boundary(dev); if (!boundary) return false; /* No need to update max_segment_size. see blk_queue_virt_boundary() */ blk_queue_virt_boundary(q, boundary); return true; } EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging); static int __init blk_settings_init(void) { blk_max_low_pfn = max_low_pfn - 1; blk_max_pfn = max_pfn - 1; return 0; } subsys_initcall(blk_settings_init);