Oh, 0xffff is fine for me, as long as you change it in
ata_scsiop_inq_b0 as well. Actually I think replacing it with a macro
(as suggested by Martin in another thread) is a good idea as well. A
line split would be better than introducing an unnecessary variable
that costs readability in the logic sense.

On 23 August 2016 at 03:51, Shaun Tancheff [off-list ref] wrote:

On Mon, Aug 22, 2016 at 2:27 PM, Tom Yan [off-list ref] wrote:

quoted

On 22 August 2016 at 12:23, Shaun Tancheff [off-list ref] wrote:

quoted

Safely overwriting the attached page to ATA format from the SCSI formatted
variant.

Signed-off-by: Shaun Tancheff <redacted>
---
v6:
 - Fix bisect bug reported by Tom Yan [off-list ref]
 - Change to use sg_copy_from_buffer as per Christoph Hellwig [off-list ref]
v5:
 - Added prep patch to work with non-page aligned scatterlist pages
   and use kmap_atomic() to lock page during modification.

 drivers/ata/libata-scsi.c | 56 ++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/ata.h       | 26 ----------------------
 2 files changed, 51 insertions(+), 31 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index e207b33..7990cb2 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c

@@ -3282,6 +3282,54 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
        return 1;
 }

+/**
+ * ata_format_dsm_trim_descr() - SATL Write Same to DSM Trim
+ * @cmd: SCSI command being translated
+ * @num: Maximum number of entries (nominally 64).
+ * @sector: Starting sector
+ * @count: Total Range of request
+ *
+ * Rewrite the WRITE SAME descriptor to be a DSM TRIM little-endian formatted
+ * descriptor.
+ *
+ * Upto 64 entries of the format:
+ *   63:48 Range Length
+ *   47:0  LBA
+ *
+ *  Range Length of 0 is ignored.
+ *  LBA's should be sorted order and not overlap.
+ *
+ * NOTE: this is the same format as ADD LBA(S) TO NV CACHE PINNED SET
+ */
+static unsigned int ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 num,
+                                             u64 sector, u32 count)
+{
+       __le64 *buffer;
+       u32 i = 0, used_bytes;
+       unsigned long flags;
+
+       BUILD_BUG_ON(512 > ATA_SCSI_RBUF_SIZE);
+
+       spin_lock_irqsave(&ata_scsi_rbuf_lock, flags);
+       buffer = ((void *)ata_scsi_rbuf);
+       while (i < num) {
+               u64 entry = sector |
+                       ((u64)(count > 0xffff ? 0xffff : count) << 48);
+               buffer[i++] = __cpu_to_le64(entry);
+               if (count <= 0xffff)
+                       break;
+               count -= 0xffff;
+               sector += 0xffff;
+       }
+
+       used_bytes = ALIGN(i * 8, 512);
+       memset(buffer + i, 0, used_bytes - i * 8);
+       sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buffer, 512);
+       spin_unlock_irqrestore(&ata_scsi_rbuf_lock, flags);
+
+       return used_bytes;
+}
+
 static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 {
        struct ata_taskfile *tf = &qc->tf;

@@ -3290,8 +3338,8 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
        const u8 *cdb = scmd->cmnd;
        u64 block;
        u32 n_block;
+       const u32 trmax = ATA_MAX_TRIM_RNUM;

This does not seem like a good idea.

quoted

        u32 size;
-       void *buf;
        u16 fp;
        u8 bp = 0xff;

@@ -3319,10 +3367,8 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
        if (!scsi_sg_count(scmd))
                goto invalid_param_len;

-       buf = page_address(sg_page(scsi_sglist(scmd)));
-
-       if (n_block <= 65535 * ATA_MAX_TRIM_RNUM) {
-               size = ata_set_lba_range_entries(buf, ATA_MAX_TRIM_RNUM, block, n_block);
+       if (n_block <= 0xffff * trmax) {

Note that the limit here would always be the advertised Maximum Write
Same Length (ata_scsiop_inq_b0). It would be best for them to look the
same. Besides, it doesn't seem necessary to create this trmax anyway.

It is entirely a style thing. I tend to prefer hex when describing an interface
that specifies number of bits. The trmax is just to keep the following line
under 80 chars.
I am not tied to either. I can change it if people really find it confusing.

quoted

quoted

+               size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block);
        } else {
                fp = 2;
                goto invalid_fld;

diff --git a/include/linux/ata.h b/include/linux/ata.h
index adbc812..45a1d71 100644
--- a/include/linux/ata.h
+++ b/include/linux/ata.h

@@ -1071,32 +1071,6 @@ static inline void ata_id_to_hd_driveid(u16 *id)
 #endif
 }

-/*
- * Write LBA Range Entries to the buffer that will cover the extent from
- * sector to sector + count.  This is used for TRIM and for ADD LBA(S)
- * TO NV CACHE PINNED SET.
- */
-static inline unsigned ata_set_lba_range_entries(void *_buffer,
-               unsigned num, u64 sector, unsigned long count)
-{
-       __le64 *buffer = _buffer;
-       unsigned i = 0, used_bytes;
-
-       while (i < num) {
-               u64 entry = sector |
-                       ((u64)(count > 0xffff ? 0xffff : count) << 48);
-               buffer[i++] = __cpu_to_le64(entry);
-               if (count <= 0xffff)
-                       break;
-               count -= 0xffff;
-               sector += 0xffff;
-       }
-
-       used_bytes = ALIGN(i * 8, 512);
-       memset(buffer + i, 0, used_bytes - i * 8);
-       return used_bytes;
-}
-
 static inline bool ata_ok(u8 status)
 {
        return ((status & (ATA_BUSY | ATA_DRDY | ATA_DF | ATA_DRQ | ATA_ERR))
--

2.9.3

--
Shaun Tancheff