catalog_read() implements the read interface for the sysfs file
/sys/bus/event_source/devices/hv_24x7/interface/catalog
It essentially takes a buffer, an offset and count as parameters
to the read() call. It makes a hypervisor call to read a specific
page from the catalog and copy the required bytes into the given
buffer. Each call to catalog_read() returns at most one 4K page.
Given these requirements, we should be able to simplify the
catalog_read().
Signed-off-by: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
---
arch/powerpc/perf/hv-24x7.c | 92 +++++----------------------------------------
1 file changed, 10 insertions(+), 82 deletions(-)
diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index 2f2215c..9427ef7 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -75,86 +75,6 @@ static struct attribute_group format_group = {
static struct kmem_cache *hv_page_cache;
-/*
- * read_offset_data - copy data from one buffer to another while treating the
- * source buffer as a small view on the total avaliable
- * source data.
- *
- * @dest: buffer to copy into
- * @dest_len: length of @dest in bytes
- * @requested_offset: the offset within the source data we want. Must be > 0
- * @src: buffer to copy data from
- * @src_len: length of @src in bytes
- * @source_offset: the offset in the sorce data that (src,src_len) refers to.
- * Must be > 0
- *
- * returns the number of bytes copied.
- *
- * The following ascii art shows the various buffer possitioning we need to
- * handle, assigns some arbitrary varibles to points on the buffer, and then
- * shows how we fiddle with those values to get things we care about (copy
- * start in src and copy len)
- *
- * s = @src buffer
- * d = @dest buffer
- * '.' areas in d are written to.
- *
- * u
- * x w v z
- * d |.........|
- * s |----------------------|
- *
- * u
- * x w z v
- * d |........------|
- * s |------------------|
- *
- * x w u,z,v
- * d |........|
- * s |------------------|
- *
- * x,w u,v,z
- * d |..................|
- * s |------------------|
- *
- * x u
- * w v z
- * d |........|
- * s |------------------|
- *
- * x z w v
- * d |------|
- * s |------|
- *
- * x = source_offset
- * w = requested_offset
- * z = source_offset + src_len
- * v = requested_offset + dest_len
- *
- * w_offset_in_s = w - x = requested_offset - source_offset
- * z_offset_in_s = z - x = src_len
- * v_offset_in_s = v - x = request_offset + dest_len - src_len
- */
-static ssize_t read_offset_data(void *dest, size_t dest_len,
- loff_t requested_offset, void *src,
- size_t src_len, loff_t source_offset)
-{
- size_t w_offset_in_s = requested_offset - source_offset;
- size_t z_offset_in_s = src_len;
- size_t v_offset_in_s = requested_offset + dest_len - src_len;
- size_t u_offset_in_s = min(z_offset_in_s, v_offset_in_s);
- size_t copy_len = u_offset_in_s - w_offset_in_s;
-
- if (requested_offset < 0 || source_offset < 0)
- return -EINVAL;
-
- if (z_offset_in_s <= w_offset_in_s)
- return 0;
-
- memcpy(dest, src + w_offset_in_s, copy_len);
- return copy_len;
-}
-
static unsigned long h_get_24x7_catalog_page_(unsigned long phys_4096,
unsigned long version,
unsigned long index)
@@ -185,6 +105,8 @@ static ssize_t catalog_read(struct file *filp, struct
kobject *kobj,
ssize_t ret = 0;
size_t catalog_len = 0, catalog_page_len = 0, page_count = 0;
loff_t page_offset = 0;
+ loff_t offset_in_page;
+ size_t copy_len;
uint64_t catalog_version_num = 0;
void *page = kmem_cache_alloc(hv_page_cache, GFP_USER);
struct hv_24x7_catalog_page_0 *page_0 = page;
@@ -203,6 +125,7 @@ static ssize_t catalog_read(struct file *filp, struct
kobject *kobj,
page_offset = offset / 4096;
page_count = count / 4096;
+ offset_in_page = count % 4096;
if (page_offset >= catalog_page_len)
goto e_free;
@@ -216,8 +139,13 @@ static ssize_t catalog_read(struct file *filp, struct
kobject *kobj,
}
}
- ret = read_offset_data(buf, count, offset,
- page, 4096, page_offset * 4096);
+ copy_len = 4096 - offset_in_page;
+ if (copy_len > count)
+ copy_len = count;
+
+ memcpy(buf, page+offset_in_page, copy_len);
+ ret = copy_len;
+
e_free:
if (hret)
pr_err("h_get_24x7_catalog_page(ver=%lld, page=%lld) failed:"
--
1.8.3.1
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