From: Tom Yan <tom.ty89@xxxxxxxxx>
Currently block layer limit max_hw_sectors is set to
ATA_MAX_SECTORS_LBA48 (65535), for devices with LBA48 support.
However, block layer limit max_sectors (which is the effective
one; also adjustable, upper-bounded by max_hw_sectors) is set to
BLK_DEF_MAX_SECTORS (currently 2560) by the scsi disk driver,
since libata's SATL does not report an Optimal Transfer Length.
This does not make much sense, especially when the current
BLK_DEF_MAX_SECTORS appears to be unsafe for some ATA devices
(see ATA_HORKAGE_MAX_SEC_1024). Truth is, the current value
appears to be arbitrary anyway. See commit d2be537c3ba3
("block: bump BLK_DEF_MAX_SECTORS to 2560").
Therefore, avoid setting dev->max_sectors when it is strictly
necessary. Leave it as 0 otherwise, so that both block layer
limits will remain as SCSI_DEFAULT_MAX_SECTORS (currently 1024).
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 0749f71..07259d8 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2610,10 +2610,8 @@ int ata_dev_configure(struct ata_device *dev)
dma_dir_string);
}
- /* determine max_sectors */
- dev->max_sectors = ATA_MAX_SECTORS;
- if (dev->flags & ATA_DFLAG_LBA48)
- dev->max_sectors = ATA_MAX_SECTORS_LBA48;
+ if (!(dev->flags & ATA_DFLAG_LBA48))
+ dev->max_sectors = ATA_MAX_SECTORS;
/* Limit PATA drive on SATA cable bridge transfers to udma5,
200 sectors */
--
2.9.2
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