Commit ea263c7f authored by Mike Christie's avatar Mike Christie Committed by Nicholas Bellinger

target: Fix max_unmap_lba_count calc overflow

max_discard_sectors only 32bits, and some non scsi backend
devices will set this to the max 0xffffffff, so we can end up
overflowing during the max_unmap_lba_count calculation.

This fixes a regression caused by my patch:

commit 8a9ebe71
Author: Mike Christie <>
Date:   Mon Jan 18 14:09:27 2016 -0600

    target: Fix WRITE_SAME/DISCARD conversion to linux 512b sectors

which can result in extra discards being sent to due the overflow
causing max_unmap_lba_count to be smaller than what the backing
device can actually support.
Signed-off-by: default avatarMike Christie <>
Reviewed-by: default avatarBart Van Assche <>
Signed-off-by: default avatarNicholas Bellinger <>
parent 064cdd2d
......@@ -821,13 +821,15 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
* in ATA and we need to set TPE=1
bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
struct request_queue *q, int block_size)
struct request_queue *q)
int block_size = queue_logical_block_size(q);
if (!blk_queue_discard(q))
return false;
attrib->max_unmap_lba_count = (q->limits.max_discard_sectors << 9) /
attrib->max_unmap_lba_count =
q->limits.max_discard_sectors >> (ilog2(block_size) - 9);
* Currently hardcoded to 1 in Linux/SCSI code..
......@@ -161,8 +161,7 @@ static int fd_configure_device(struct se_device *dev)
dev_size, div_u64(dev_size, fd_dev->fd_block_size),
if (target_configure_unmap_from_queue(&dev->dev_attrib, q,
if (target_configure_unmap_from_queue(&dev->dev_attrib, q))
pr_debug("IFILE: BLOCK Discard support available,"
" disabled by default\n");
......@@ -121,8 +121,7 @@ static int iblock_configure_device(struct se_device *dev)
dev->dev_attrib.hw_max_sectors = queue_max_hw_sectors(q);
dev->dev_attrib.hw_queue_depth = q->nr_requests;
if (target_configure_unmap_from_queue(&dev->dev_attrib, q,
if (target_configure_unmap_from_queue(&dev->dev_attrib, q))
pr_debug("IBLOCK: BLOCK Discard support available,"
" disabled by default\n");
......@@ -95,6 +95,6 @@ sense_reason_t passthrough_parse_cdb(struct se_cmd *cmd,
bool target_sense_desc_format(struct se_device *dev);
sector_t target_to_linux_sector(struct se_device *dev, sector_t lb);
bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
struct request_queue *q, int block_size);
struct request_queue *q);
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