ata: libata-scsi: fix DSM TRIM for sector sizes larger than 2048 bytes

ata_scsi_write_same_xlat() translates a SCSI WRITE SAME command with the
UNMAP bit set into an ATA DATA SET MANAGEMENT TRIM command.  The TRIM
descriptor is built by ata_format_dsm_trim_descr() into the 2048-byte
ata_scsi_rbuf staging buffer, and the number of bytes copied is compared
against the logical sector size by the caller:

	size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block);
	if (size != len)		/* len == sdp->sector_size */
		goto invalid_param_len;

ata_format_dsm_trim_descr() clamps the copy length to ATA_SCSI_RBUF_SIZE
(2048).  On a device whose logical sector size exceeds that (e.g. a 4Kn
device, where sector_size == 4096) the function can never return more than
2048, while the caller expects it to return sector_size.  The comparison
therefore always fails, so every TRIM is rejected with "Parameter list
length error" and WARN_ON() splats on each attempt.  TRIM / discard is
thus completely broken on such devices.

The descriptor was incorrectly sized from the logical sector size.  A DSM
TRIM payload is a list of 512-byte pages, each holding up to
ATA_MAX_TRIM_RNUM (64) LBA Range Entries, and is independent of the logical
sector size.  The Block Limits VPD page already advertises a single such
page as the maximum WRITE SAME length (65535 * ATA_MAX_TRIM_RNUM logical
blocks), so the block layer never sends a request that needs more than one
page.

Emit exactly one 512-byte page, independent of the logical sector size,
and transfer only that page (COUNT == 1).  For a 512-byte-sector device
this is unchanged; devices with larger logical sectors now work instead of
failing every TRIM.

Reviewed-by: Hannes Reinecke <hare@kernel.org>
Fixes: ef2d7392c4ec ("libata: SCT Write Same / DSM Trim")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

0 files changed, 0 insertions, 0 deletions