target/file: Add WRITE_SAME w/ UNMAP=0 emulation support

This patch adds support for emulation of WRITE_SAME w/ UNMAP=0 within
fd_execute_write_same() backend code.

The emulation uses vfs_writev() to submit a locally populated buffer
from the received WRITE_SAME scatterlist block for duplication, and by
default enforces a limit of max_write_same_len=0x1000 (8192) sectors up
to the limit of 1024 iovec entries for the single call to vfs_writev().

It also sets max_write_same_len to the operational default at setup ->
fd_configure_device() time.

Tested with 512, 1k, 2k, and 4k block_sizes.

(asias: convert to vzalloc)

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Asias He <asias@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 114 insertions, 0 deletions

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index b9c88497e8f0..94383a56bd74 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -190,6 +190,11 @@ static int fd_configure_device(struct se_device *dev)
 
         fd_dev->fd_dev_id = fd_host->fd_host_dev_id_count++;
         fd_dev->fd_queue_depth = dev->queue_depth;
+        /*
+         * Limit WRITE_SAME w/ UNMAP=0 emulation to 8k Number of LBAs (NoLB)
+         * based upon struct iovec limit for vfs_writev()
+         */
+        dev->dev_attrib.max_write_same_len = 0x1000;
 
         pr_debug("CORE_FILE[%u] - Added TCM FILEIO Device ID: %u at %s,"
                 " %llu total bytes\n", fd_host->fd_host_id, fd_dev->fd_dev_id,
@@ -328,6 +333,114 @@ fd_execute_sync_cache(struct se_cmd *cmd)
         return 0;
 }
 
+static unsigned char *
+fd_setup_write_same_buf(struct se_cmd *cmd, struct scatterlist *sg,
+                    unsigned int len)
+{
+        struct se_device *se_dev = cmd->se_dev;
+        unsigned int block_size = se_dev->dev_attrib.block_size;
+        unsigned int i = 0, end;
+        unsigned char *buf, *p, *kmap_buf;
+
+        buf = kzalloc(min_t(unsigned int, len, PAGE_SIZE), GFP_KERNEL);
+        if (!buf) {
+                pr_err("Unable to allocate fd_execute_write_same buf\n");
+                return NULL;
+        }
+
+        kmap_buf = kmap(sg_page(sg)) + sg->offset;
+        if (!kmap_buf) {
+                pr_err("kmap() failed in fd_setup_write_same\n");
+                kfree(buf);
+                return NULL;
+        }
+        /*
+         * Fill local *buf to contain multiple WRITE_SAME blocks up to
+         * min(len, PAGE_SIZE)
+         */
+        p = buf;
+        end = min_t(unsigned int, len, PAGE_SIZE);
+
+        while (i < end) {
+                memcpy(p, kmap_buf, block_size);
+
+                i += block_size;
+                p += block_size;
+        }
+        kunmap(sg_page(sg));
+
+        return buf;
+}
+
+static sense_reason_t
+fd_execute_write_same(struct se_cmd *cmd)
+{
+        struct se_device *se_dev = cmd->se_dev;
+        struct fd_dev *fd_dev = FD_DEV(se_dev);
+        struct file *f = fd_dev->fd_file;
+        struct scatterlist *sg;
+        struct iovec *iov;
+        mm_segment_t old_fs;
+        sector_t nolb = spc_get_write_same_sectors(cmd);
+        loff_t pos = cmd->t_task_lba * se_dev->dev_attrib.block_size;
+        unsigned int len, len_tmp, iov_num;
+        int i, rc;
+        unsigned char *buf;
+
+        if (!nolb) {
+                target_complete_cmd(cmd, SAM_STAT_GOOD);
+                return 0;
+        }
+        sg = &cmd->t_data_sg[0];
+
+        if (cmd->t_data_nents > 1 ||
+            sg->length != cmd->se_dev->dev_attrib.block_size) {
+                pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"
+                        " block_size: %u\n", cmd->t_data_nents, sg->length,
+                        cmd->se_dev->dev_attrib.block_size);
+                return TCM_INVALID_CDB_FIELD;
+        }
+
+        len = len_tmp = nolb * se_dev->dev_attrib.block_size;
+        iov_num = DIV_ROUND_UP(len, PAGE_SIZE);
+
+        buf = fd_setup_write_same_buf(cmd, sg, len);
+        if (!buf)
+                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+
+        iov = vzalloc(sizeof(struct iovec) * iov_num);
+        if (!iov) {
+                pr_err("Unable to allocate fd_execute_write_same iovecs\n");
+                kfree(buf);
+                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+        }
+        /*
+         * Map the single fabric received scatterlist block now populated
+         * in *buf into each iovec for I/O submission.
+         */
+        for (i = 0; i < iov_num; i++) {
+                iov[i].iov_base = buf;
+                iov[i].iov_len = min_t(unsigned int, len_tmp, PAGE_SIZE);
+                len_tmp -= iov[i].iov_len;
+        }
+
+        old_fs = get_fs();
+        set_fs(get_ds());
+        rc = vfs_writev(f, &iov[0], iov_num, &pos);
+        set_fs(old_fs);
+
+        vfree(iov);
+        kfree(buf);
+
+        if (rc < 0 || rc != len) {
+                pr_err("vfs_writev() returned %d for write same\n", rc);
+                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+        }
+
+        target_complete_cmd(cmd, SAM_STAT_GOOD);
+        return 0;
+}
+
 static sense_reason_t
 fd_execute_rw(struct se_cmd *cmd)
 {
@@ -486,6 +599,7 @@ static sector_t fd_get_blocks(struct se_device *dev)
 static struct sbc_ops fd_sbc_ops = {
         .execute_rw             = fd_execute_rw,
         .execute_sync_cache     = fd_execute_sync_cache,
+        .execute_write_same     = fd_execute_write_same,
 };
 
 static sense_reason_t