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Subject[PATCH V2 8/8] btrfs: convert to zero_user()
Date
From: Ira Weiny <ira.weiny@intel.com>

There are many places where kmap/memset/kunmap patterns occur.

This pattern exists in the core as zero_user()

Use zero_user() to eliminate direct uses of kmap and leverage the new
core functions use of kmap_local_page().

The development of this patch was aided by the following coccinelle
script:

// <smpl>
// SPDX-License-Identifier: GPL-2.0-only
// Find kmap/memset/kunmap pattern and replace with memset*page calls
//
// NOTE: Offsets and other expressions may be more complex than what the script
// will automatically generate. Therefore a catchall rule is provided to find
// the pattern which then must be evaluated by hand.
//
// Confidence: Low
// Copyright: (C) 2021 Intel Corporation
// URL: http://coccinelle.lip6.fr/
// Comments:
// Options:

//
// Then the memset pattern
//
@ memset_rule1 @
expression page, V, L, Off;
identifier ptr;
type VP;
@@

(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
-memset(ptr, 0, L);
+zero_user(page, 0, L);
|
-memset(ptr + Off, 0, L);
+zero_user(page, Off, L);
|
-memset(ptr, V, L);
+memset_page(page, V, 0, L);
|
-memset(ptr + Off, V, L);
+memset_page(page, V, Off, L);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)

// Remove any pointers left unused
@
depends on memset_rule1
@
identifier memset_rule1.ptr;
type VP, VP1;
@@

-VP ptr;
... when != ptr;
? VP1 ptr;

//
// Catch all
//
@ memset_rule2 @
expression page;
identifier ptr;
expression GenTo, GenSize, GenValue;
type VP;
@@

(
-VP ptr = kmap(page);
|
-ptr = kmap(page);
|
-VP ptr = kmap_atomic(page);
|
-ptr = kmap_atomic(page);
)
<+...
(
//
// Some call sites have complex expressions within the memset/memcpy
// The follow are catch alls which need to be evaluated by hand.
//
-memset(GenTo, 0, GenSize);
+zero_userExtra(page, GenTo, GenSize);
|
-memset(GenTo, GenValue, GenSize);
+memset_pageExtra(page, GenValue, GenTo, GenSize);
)
...+>
(
-kunmap(page);
|
-kunmap_atomic(ptr);
)

// Remove any pointers left unused
@
depends on memset_rule2
@
identifier memset_rule2.ptr;
type VP, VP1;
@@

-VP ptr;
... when != ptr;
? VP1 ptr;

// </smpl>

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from v1:
Update commit message per David
https://lore.kernel.org/lkml/20210209151442.GU1993@suse.cz/
---
fs/btrfs/compression.c | 5 +----
fs/btrfs/extent_io.c | 22 ++++------------------
fs/btrfs/inode.c | 33 ++++++++++-----------------------
fs/btrfs/reflink.c | 6 +-----
fs/btrfs/zlib.c | 5 +----
fs/btrfs/zstd.c | 5 +----
6 files changed, 18 insertions(+), 58 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 047b632b4139..a219dcdb749e 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -567,16 +567,13 @@ static noinline int add_ra_bio_pages(struct inode *inode,
free_extent_map(em);

if (page->index == end_index) {
- char *userpage;
size_t zero_offset = offset_in_page(isize);

if (zero_offset) {
int zeros;
zeros = PAGE_SIZE - zero_offset;
- userpage = kmap_atomic(page);
- memset(userpage + zero_offset, 0, zeros);
+ zero_user(page, zero_offset, zeros);
flush_dcache_page(page);
- kunmap_atomic(userpage);
}
}

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c9cee458e001..bdc9389bff59 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3229,15 +3229,12 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
}

if (page->index == last_byte >> PAGE_SHIFT) {
- char *userpage;
size_t zero_offset = offset_in_page(last_byte);

if (zero_offset) {
iosize = PAGE_SIZE - zero_offset;
- userpage = kmap_atomic(page);
- memset(userpage + zero_offset, 0, iosize);
+ zero_user(page, zero_offset, iosize);
flush_dcache_page(page);
- kunmap_atomic(userpage);
}
}
while (cur <= end) {
@@ -3245,14 +3242,11 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
u64 offset;

if (cur >= last_byte) {
- char *userpage;
struct extent_state *cached = NULL;

iosize = PAGE_SIZE - pg_offset;
- userpage = kmap_atomic(page);
- memset(userpage + pg_offset, 0, iosize);
+ zero_user(page, pg_offset, iosize);
flush_dcache_page(page);
- kunmap_atomic(userpage);
set_extent_uptodate(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
unlock_extent_cached(tree, cur,
@@ -3334,13 +3328,10 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,

/* we've found a hole, just zero and go on */
if (block_start == EXTENT_MAP_HOLE) {
- char *userpage;
struct extent_state *cached = NULL;

- userpage = kmap_atomic(page);
- memset(userpage + pg_offset, 0, iosize);
+ zero_user(page, pg_offset, iosize);
flush_dcache_page(page);
- kunmap_atomic(userpage);

set_extent_uptodate(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
@@ -3654,12 +3645,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
}

if (page->index == end_index) {
- char *userpage;
-
- userpage = kmap_atomic(page);
- memset(userpage + pg_offset, 0,
- PAGE_SIZE - pg_offset);
- kunmap_atomic(userpage);
+ zero_user(page, pg_offset, PAGE_SIZE - pg_offset);
flush_dcache_page(page);
}

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a8e0a6b038d3..641f21a11722 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -640,17 +640,12 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
if (!ret) {
unsigned long offset = offset_in_page(total_compressed);
struct page *page = pages[nr_pages - 1];
- char *kaddr;

/* zero the tail end of the last page, we might be
* sending it down to disk
*/
- if (offset) {
- kaddr = kmap_atomic(page);
- memset(kaddr + offset, 0,
- PAGE_SIZE - offset);
- kunmap_atomic(kaddr);
- }
+ if (offset)
+ zero_user(page, offset, PAGE_SIZE - offset);
will_compress = 1;
}
}
@@ -4675,7 +4670,6 @@ int btrfs_truncate_block(struct btrfs_inode *inode, loff_t from, loff_t len,
struct btrfs_ordered_extent *ordered;
struct extent_state *cached_state = NULL;
struct extent_changeset *data_reserved = NULL;
- char *kaddr;
bool only_release_metadata = false;
u32 blocksize = fs_info->sectorsize;
pgoff_t index = from >> PAGE_SHIFT;
@@ -4765,15 +4759,13 @@ int btrfs_truncate_block(struct btrfs_inode *inode, loff_t from, loff_t len,
if (offset != blocksize) {
if (!len)
len = blocksize - offset;
- kaddr = kmap(page);
if (front)
- memset(kaddr + (block_start - page_offset(page)),
- 0, offset);
+ zero_user(page, (block_start - page_offset(page)),
+ offset);
else
- memset(kaddr + (block_start - page_offset(page)) + offset,
- 0, len);
+ zero_user(page, (block_start - page_offset(page)) + offset,
+ len);
flush_dcache_page(page);
- kunmap(page);
}
ClearPageChecked(page);
set_page_dirty(page);
@@ -6660,11 +6652,9 @@ static noinline int uncompress_inline(struct btrfs_path *path,
* cover that region here.
*/

- if (max_size + pg_offset < PAGE_SIZE) {
- char *map = kmap(page);
- memset(map + pg_offset + max_size, 0, PAGE_SIZE - max_size - pg_offset);
- kunmap(page);
- }
+ if (max_size + pg_offset < PAGE_SIZE)
+ zero_user(page, pg_offset + max_size,
+ PAGE_SIZE - max_size - pg_offset);
kfree(tmp);
return ret;
}
@@ -8303,7 +8293,6 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
struct btrfs_ordered_extent *ordered;
struct extent_state *cached_state = NULL;
struct extent_changeset *data_reserved = NULL;
- char *kaddr;
unsigned long zero_start;
loff_t size;
vm_fault_t ret;
@@ -8410,10 +8399,8 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
zero_start = PAGE_SIZE;

if (zero_start != PAGE_SIZE) {
- kaddr = kmap(page);
- memset(kaddr + zero_start, 0, PAGE_SIZE - zero_start);
+ zero_user(page, zero_start, PAGE_SIZE - zero_start);
flush_dcache_page(page);
- kunmap(page);
}
ClearPageChecked(page);
set_page_dirty(page);
diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index 74c62e49c0c9..c052c4878670 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -126,12 +126,8 @@ static int copy_inline_to_page(struct btrfs_inode *inode,
* So what's in the range [500, 4095] corresponds to zeroes.
*/
if (datal < block_size) {
- char *map;
-
- map = kmap(page);
- memset(map + datal, 0, block_size - datal);
+ zero_user(page, datal, block_size - datal);
flush_dcache_page(page);
- kunmap(page);
}

SetPageUptodate(page);
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index d524acf7b3e5..fd612a509463 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -375,7 +375,6 @@ int zlib_decompress(struct list_head *ws, unsigned char *data_in,
unsigned long bytes_left;
unsigned long total_out = 0;
unsigned long pg_offset = 0;
- char *kaddr;

destlen = min_t(unsigned long, destlen, PAGE_SIZE);
bytes_left = destlen;
@@ -455,9 +454,7 @@ int zlib_decompress(struct list_head *ws, unsigned char *data_in,
* end of the inline extent (destlen) to the end of the page
*/
if (pg_offset < destlen) {
- kaddr = kmap_atomic(dest_page);
- memset(kaddr + pg_offset, 0, destlen - pg_offset);
- kunmap_atomic(kaddr);
+ zero_user(dest_page, pg_offset, destlen - pg_offset);
}
return ret;
}
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 8e9626d63976..b6f687b8a3da 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -631,7 +631,6 @@ int zstd_decompress(struct list_head *ws, unsigned char *data_in,
size_t ret2;
unsigned long total_out = 0;
unsigned long pg_offset = 0;
- char *kaddr;

stream = ZSTD_initDStream(
ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
@@ -696,9 +695,7 @@ int zstd_decompress(struct list_head *ws, unsigned char *data_in,
ret = 0;
finish:
if (pg_offset < destlen) {
- kaddr = kmap_atomic(dest_page);
- memset(kaddr + pg_offset, 0, destlen - pg_offset);
- kunmap_atomic(kaddr);
+ zero_user(dest_page, pg_offset, destlen - pg_offset);
}
return ret;
}
--
2.28.0.rc0.12.gb6a658bd00c9
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