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@@ -212,26 +212,30 @@ EXPORT_SYMBOL(blk_queue_bounce_limit);
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/**
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* blk_queue_max_sectors - set max sectors for a request for this queue
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* @q: the request queue for the device
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- * @max_sectors: max sectors in the usual 512b unit
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+ * @max_hw_sectors: max hardware sectors in the usual 512b unit
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*
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* Description:
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- * Enables a low level driver to set an upper limit on the size of
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- * received requests.
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+ * Enables a low level driver to set a hard upper limit,
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+ * max_hw_sectors, on the size of requests. max_hw_sectors is set by
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+ * the device driver based upon the combined capabilities of I/O
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+ * controller and storage device.
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+ *
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+ * max_sectors is a soft limit imposed by the block layer for
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+ * filesystem type requests. This value can be overridden on a
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+ * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
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+ * The soft limit can not exceed max_hw_sectors.
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**/
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-void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
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+void blk_queue_max_sectors(struct request_queue *q, unsigned int max_hw_sectors)
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{
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- if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
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- max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
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+ if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
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+ max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
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printk(KERN_INFO "%s: set to minimum %d\n",
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- __func__, max_sectors);
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+ __func__, max_hw_sectors);
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}
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- if (BLK_DEF_MAX_SECTORS > max_sectors)
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- q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;
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- else {
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- q->limits.max_sectors = BLK_DEF_MAX_SECTORS;
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- q->limits.max_hw_sectors = max_sectors;
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- }
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+ q->limits.max_hw_sectors = max_hw_sectors;
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+ q->limits.max_sectors = min_t(unsigned int, max_hw_sectors,
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+ BLK_DEF_MAX_SECTORS);
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}
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EXPORT_SYMBOL(blk_queue_max_sectors);
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