Revert "libata: switch to dynamic allocation instead of ata_scsi_rbuf"

This reverts commit a234f739.

The commit tried to get rid of the shared global SCSI response buffer.
Unfortunately, it added blocking allocation to atomic path.  Revert it
for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>

drivers/ata/libata-scsi.c

@@ -57,6 +57,9 @@
 
 #define ATA_SCSI_RBUF_SIZE	4096
 
+static DEFINE_SPINLOCK(ata_scsi_rbuf_lock);
+static u8 ata_scsi_rbuf[ATA_SCSI_RBUF_SIZE];
+
 typedef unsigned int (*ata_xlat_func_t)(struct ata_queued_cmd *qc);
 
 static struct ata_device *__ata_scsi_find_dev(struct ata_port *ap,
@@ -2053,6 +2056,53 @@ struct ata_scsi_args {
 	struct scsi_cmnd	*cmd;
 };
 
+/**
+ *	ata_scsi_rbuf_get - Map response buffer.
+ *	@cmd: SCSI command containing buffer to be mapped.
+ *	@flags: unsigned long variable to store irq enable status
+ *	@copy_in: copy in from user buffer
+ *
+ *	Prepare buffer for simulated SCSI commands.
+ *
+ *	LOCKING:
+ *	spin_lock_irqsave(ata_scsi_rbuf_lock) on success
+ *
+ *	RETURNS:
+ *	Pointer to response buffer.
+ */
+static void *ata_scsi_rbuf_get(struct scsi_cmnd *cmd, bool copy_in,
+			       unsigned long *flags)
+{
+	spin_lock_irqsave(&ata_scsi_rbuf_lock, *flags);
+
+	memset(ata_scsi_rbuf, 0, ATA_SCSI_RBUF_SIZE);
+	if (copy_in)
+		sg_copy_to_buffer(scsi_sglist(cmd), scsi_sg_count(cmd),
+				  ata_scsi_rbuf, ATA_SCSI_RBUF_SIZE);
+	return ata_scsi_rbuf;
+}
+
+/**
+ *	ata_scsi_rbuf_put - Unmap response buffer.
+ *	@cmd: SCSI command containing buffer to be unmapped.
+ *	@copy_out: copy out result
+ *	@flags: @flags passed to ata_scsi_rbuf_get()
+ *
+ *	Returns rbuf buffer.  The result is copied to @cmd's buffer if
+ *	@copy_back is true.
+ *
+ *	LOCKING:
+ *	Unlocks ata_scsi_rbuf_lock.
+ */
+static inline void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, bool copy_out,
+				     unsigned long *flags)
+{
+	if (copy_out)
+		sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd),
+				    ata_scsi_rbuf, ATA_SCSI_RBUF_SIZE);
+	spin_unlock_irqrestore(&ata_scsi_rbuf_lock, *flags);
+}
+
 /**
  *	ata_scsi_rbuf_fill - wrapper for SCSI command simulators
  *	@args: device IDENTIFY data / SCSI command of interest.
@@ -2071,22 +2121,17 @@ struct ata_scsi_args {
 static void ata_scsi_rbuf_fill(struct ata_scsi_args *args,
 		unsigned int (*actor)(struct ata_scsi_args *args, u8 *rbuf))
 {
+	u8 *rbuf;
+	unsigned int rc;
 	struct scsi_cmnd *cmd = args->cmd;
-	u8 *buf;
+	unsigned long flags;
 
-	buf = kzalloc(ATA_SCSI_RBUF_SIZE, GFP_NOIO);
-	if (!buf) {
-		ata_scsi_set_sense(args->dev, cmd, NOT_READY, 0x08, 0);
-		return;
-	}
+	rbuf = ata_scsi_rbuf_get(cmd, false, &flags);
+	rc = actor(args, rbuf);
+	ata_scsi_rbuf_put(cmd, rc == 0, &flags);
 
-	if (actor(args, buf) == 0) {
-		sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd),
-				    buf, ATA_SCSI_RBUF_SIZE);
+	if (rc == 0)
 		cmd->result = SAM_STAT_GOOD;
-	}
-
-	kfree(buf);
 }
 
 /**
@@ -3318,17 +3363,24 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
  *
  * Return: Number of bytes copied into sglist.
  */
-static ssize_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax,
+static size_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax,
 					u64 sector, u32 count)
 {
+	struct scsi_device *sdp = cmd->device;
+	size_t len = sdp->sector_size;
 	size_t r;
 	__le64 *buf;
 	u32 i = 0;
+	unsigned long flags;
 
-	buf = kzalloc(cmd->device->sector_size, GFP_NOFS);
-	if (!buf)
-		return -ENOMEM;
+	WARN_ON(len > ATA_SCSI_RBUF_SIZE);
 
+	if (len > ATA_SCSI_RBUF_SIZE)
+		len = ATA_SCSI_RBUF_SIZE;
+
+	spin_lock_irqsave(&ata_scsi_rbuf_lock, flags);
+	buf = ((void *)ata_scsi_rbuf);
+	memset(buf, 0, len);
 	while (i < trmax) {
 		u64 entry = sector |
 			((u64)(count > 0xffff ? 0xffff : count) << 48);
@@ -3338,9 +3390,9 @@ static ssize_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax,
 		count -= 0xffff;
 		sector += 0xffff;
 	}
-	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf,
-			cmd->device->sector_size);
-	kfree(buf);
+	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, len);
+	spin_unlock_irqrestore(&ata_scsi_rbuf_lock, flags);
+
 	return r;
 }
 
@@ -3356,15 +3408,16 @@ static ssize_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax,
  *
  * Return: Number of bytes copied into sglist.
  */
-static ssize_t ata_format_sct_write_same(struct scsi_cmnd *cmd, u64 lba,
-		u64 num)
+static size_t ata_format_sct_write_same(struct scsi_cmnd *cmd, u64 lba, u64 num)
 {
+	struct scsi_device *sdp = cmd->device;
+	size_t len = sdp->sector_size;
 	size_t r;
 	u16 *buf;
+	unsigned long flags;
 
-	buf = kzalloc(cmd->device->sector_size, GFP_NOIO);
-	if (!buf)
-		return -ENOMEM;
+	spin_lock_irqsave(&ata_scsi_rbuf_lock, flags);
+	buf = ((void *)ata_scsi_rbuf);
 
 	put_unaligned_le16(0x0002,  &buf[0]); /* SCT_ACT_WRITE_SAME */
 	put_unaligned_le16(0x0101,  &buf[1]); /* WRITE PTRN FG */
@@ -3372,9 +3425,14 @@ static ssize_t ata_format_sct_write_same(struct scsi_cmnd *cmd, u64 lba,
 	put_unaligned_le64(num,     &buf[6]);
 	put_unaligned_le32(0u,      &buf[10]); /* pattern */
 
-	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf,
-			cmd->device->sector_size);
-	kfree(buf);
+	WARN_ON(len > ATA_SCSI_RBUF_SIZE);
+
+	if (len > ATA_SCSI_RBUF_SIZE)
+		len = ATA_SCSI_RBUF_SIZE;
+
+	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, len);
+	spin_unlock_irqrestore(&ata_scsi_rbuf_lock, flags);
+
 	return r;
 }
 
@@ -3399,7 +3457,7 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 	u64 block;
 	u32 n_block;
 	const u32 trmax = len >> 3;
-	ssize_t size;
+	u32 size;
 	u16 fp;
 	u8 bp = 0xff;
 	u8 unmap = cdb[1] & 0x8;
@@ -3450,8 +3508,6 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 	 */
 	if (unmap) {
 		size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block);
-		if (size < 0)
-			goto comm_fail;
 		if (size != len)
 			goto invalid_param_len;
 
@@ -3475,8 +3531,6 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 		}
 	} else {
 		size = ata_format_sct_write_same(scmd, block, n_block);
-		if (size < 0)
-			goto comm_fail;
 		if (size != len)
 			goto invalid_param_len;
 
@@ -3515,10 +3569,6 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 	/* "Invalid command operation code" */
 	ata_scsi_set_sense(dev, scmd, ILLEGAL_REQUEST, 0x20, 0x0);
 	return 1;
-comm_fail:
-	/* "Logical unit communication failure" */
-	ata_scsi_set_sense(dev, scmd, NOT_READY, 0x08, 0);
-	return 1;
 }
 
 /**