[PATCH V2 4/6] Add support to lseek /proc/<pid>/numa_vamaps file

[Prakash Sangappa]

Allow lseeking to a process virtual address(VA), starting from where
the address range to numa node information can be read. The lseek offset
will be the process virtual address.

Signed-off-by: Prakash Sangappa <prakash.sangappa@xxxxxxxxxx>
Reviewed-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
---
 fs/proc/task_mmu.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1371e379..93dce46 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1866,6 +1866,27 @@ static int gather_hole_info_vamap(unsigned long start, unsigned long end,
 	return 0;
 }
 
+static loff_t numa_vamaps_llseek(struct file *file, loff_t offset, int orig)
+{
+	struct numa_vamaps_private *nvm = file->private_data;
+
+	if (orig == SEEK_CUR && offset < 0 && nvm->vm_start < -offset)
+		return -EINVAL;
+
+	switch (orig) {
+	case SEEK_SET:
+		nvm->vm_start = offset & PAGE_MASK;
+		break;
+	case SEEK_CUR:
+		nvm->vm_start += offset;
+		nvm->vm_start = nvm->vm_start & PAGE_MASK;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return nvm->vm_start;
+}
+
 static int vamap_vprintf(struct numa_vamaps_private *nvm, const char *f, ...)
 {
 	va_list args;
@@ -2052,7 +2073,7 @@ const struct file_operations proc_pid_numa_maps_operations = {
 const struct file_operations proc_numa_vamaps_operations = {
 	.open		= numa_vamaps_open,
 	.read		= numa_vamaps_read,
-	.llseek		= noop_llseek,
+	.llseek		= numa_vamaps_llseek,
 	.release	= numa_vamaps_release,
 };
 #endif /* CONFIG_NUMA */
-- 
2.7.4