target/file: Fix 32-bit highmem breakage for SGL -> iovec mapping

This patch changes vectored file I/O to use kmap + kunmap when mapping
incoming SGL memory -> struct iovec in order to properly support 32-bit
highmem configurations.  This is because an extra bounce buffer may be
required when processing scatterlist pages allocated with GFP_KERNEL.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index 8f6dae074c2c..1fc5825b3912 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -236,7 +236,7 @@ static int fd_do_readv(struct se_cmd *cmd, struct scatterlist *sgl,
 
         for_each_sg(sgl, sg, sgl_nents, i) {
                 iov[i].iov_len = sg->length;
-                iov[i].iov_base = sg_virt(sg);
+                iov[i].iov_base = kmap(sg_page(sg)) + sg->offset;
         }
 
         old_fs = get_fs();
@@ -244,6 +244,8 @@ static int fd_do_readv(struct se_cmd *cmd, struct scatterlist *sgl,
         ret = vfs_readv(fd, &iov[0], sgl_nents, &pos);
         set_fs(old_fs);
 
+        for_each_sg(sgl, sg, sgl_nents, i)
+                kunmap(sg_page(sg));
         kfree(iov);
         /*
          * Return zeros and GOOD status even if the READ did not return
@@ -288,7 +290,7 @@ static int fd_do_writev(struct se_cmd *cmd, struct scatterlist *sgl,
 
         for_each_sg(sgl, sg, sgl_nents, i) {
                 iov[i].iov_len = sg->length;
-                iov[i].iov_base = sg_virt(sg);
+                iov[i].iov_base = kmap(sg_page(sg)) + sg->offset;
         }
 
         old_fs = get_fs();
@@ -296,6 +298,9 @@ static int fd_do_writev(struct se_cmd *cmd, struct scatterlist *sgl,
         ret = vfs_writev(fd, &iov[0], sgl_nents, &pos);
         set_fs(old_fs);
 
+        for_each_sg(sgl, sg, sgl_nents, i)
+                kunmap(sg_page(sg));
+
         kfree(iov);
 
         if (ret < 0 || ret != cmd->data_length) {