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

commit 40ff2c3b3da35dd3a00ac6722056a59b4b3f2caf upstream.

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>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
[bwh: Backported to 3.2: use task->task_sg{,_nents} for iteration]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index a251efd783de1e612c1740fafc37c72169ca3100..f44459a2a7c526c0292667b543d381f7155d9d9a 100644 (file)
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -299,7 +299,7 @@ static int fd_do_readv(struct se_task *task)
 
        for_each_sg(task->task_sg, sg, task->task_sg_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();
@@ -307,6 +307,8 @@ static int fd_do_readv(struct se_task *task)
        ret = vfs_readv(fd, &iov[0], task->task_sg_nents, &pos);
        set_fs(old_fs);
 
+       for_each_sg(task->task_sg, sg, task->task_sg_nents, i)
+               kunmap(sg_page(sg));
        kfree(iov);
        /*
         * Return zeros and GOOD status even if the READ did not return
@@ -352,7 +354,7 @@ static int fd_do_writev(struct se_task *task)
 
        for_each_sg(task->task_sg, sg, task->task_sg_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();
@@ -360,6 +362,9 @@ static int fd_do_writev(struct se_task *task)
        ret = vfs_writev(fd, &iov[0], task->task_sg_nents, &pos);
        set_fs(old_fs);
 
+       for_each_sg(task->task_sg, sg, task->task_sg_nents, i)
+               kunmap(sg_page(sg));
+
        kfree(iov);
 
        if (ret < 0 || ret != task->task_size) {