[PATCHv6 18/37] fs: make block_write_{begin,end}() be able to handle huge pages

Kirill A. Shutemov
2017-01-26T11:58:00Z

It's more or less straight-forward.

Most changes are around getting offset/len withing page right and zero
out desired part of the page.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/buffer.c | 70 +++++++++++++++++++++++++++++++++++--------------------------
1 file changed, 40 insertions(+), 30 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 72462beca909..d05524f14846 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1902,6 +1902,7 @@ void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
unsigned int block_start, block_end;
struct buffer_head *head, *bh;
+ bool uptodate = PageUptodate(page);

BUG_ON(!PageLocked(page));
if (!page_has_buffers(page))
@@ -1912,21 +1913,21 @@ void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
do {
block_end = block_start + bh->b_size;

- if (buffer_new(bh)) {
- if (block_end > from && block_start < to) {
- if (!PageUptodate(page)) {
- unsigned start, size;
+ if (buffer_new(bh) && block_end > from && block_start < to) {
+ if (!uptodate) {
+ unsigned start, size;

- start = max(from, block_start);
- size = min(to, block_end) - start;
+ start = max(from, block_start);
+ size = min(to, block_end) - start;

- zero_user(page, start, size);
- set_buffer_uptodate(bh);
- }
-
- clear_buffer_new(bh);
- mark_buffer_dirty(bh);
+ zero_user(page + block_start / PAGE_SIZE,
+ start % PAGE_SIZE,
+ size);
+ set_buffer_uptodate(bh);
}
+
+ clear_buffer_new(bh);
+ mark_buffer_dirty(bh);
}

block_start = block_end;
@@ -1992,18 +1993,21 @@ iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
get_block_t *get_block, struct iomap *iomap)
{
- unsigned from = pos & (PAGE_SIZE - 1);
- unsigned to = from + len;
- struct inode *inode = page->mapping->host;
+ unsigned from, to;
+ struct inode *inode = page_mapping(page)->host;
unsigned block_start, block_end;
sector_t block;
int err = 0;
unsigned blocksize, bbits;
struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
+ bool uptodate = PageUptodate(page);

+ page = compound_head(page);
+ from = pos & ~hpage_mask(page);
+ to = from + len;
BUG_ON(!PageLocked(page));
- BUG_ON(from > PAGE_SIZE);
- BUG_ON(to > PAGE_SIZE);
+ BUG_ON(from > hpage_size(page));
+ BUG_ON(to > hpage_size(page));
BUG_ON(from > to);

head = create_page_buffers(page, inode, 0);
@@ -2016,10 +2020,8 @@ int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
block++, block_start=block_end, bh = bh->b_this_page) {
block_end = block_start + blocksize;
if (block_end <= from || block_start >= to) {
- if (PageUptodate(page)) {
- if (!buffer_uptodate(bh))
- set_buffer_uptodate(bh);
- }
+ if (uptodate && !buffer_uptodate(bh))
+ set_buffer_uptodate(bh);
continue;
}
if (buffer_new(bh))
@@ -2036,23 +2038,28 @@ int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,

if (buffer_new(bh)) {
clean_bdev_bh_alias(bh);
- if (PageUptodate(page)) {
+ if (uptodate) {
clear_buffer_new(bh);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
continue;
}
- if (block_end > to || block_start < from)
- zero_user_segments(page,
- to, block_end,
- block_start, from);
+ if (block_end > to || block_start < from) {
+ BUG_ON(to - from > PAGE_SIZE);
+ zero_user_segments(page +
+ block_start / PAGE_SIZE,
+ to % PAGE_SIZE,
+ (block_start % PAGE_SIZE) + blocksize,
+ block_start % PAGE_SIZE,
+ from % PAGE_SIZE);
+ }
continue;
}
}
- if (PageUptodate(page)) {
+ if (uptodate) {
if (!buffer_uptodate(bh))
set_buffer_uptodate(bh);
- continue;
+ continue;
}
if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
!buffer_unwritten(bh) &&
@@ -2089,6 +2096,7 @@ static int __block_commit_write(struct inode *inode, struct page *page,
unsigned blocksize;
struct buffer_head *bh, *head;

+ VM_BUG_ON_PAGE(PageTail(page), page);
bh = head = page_buffers(page);
blocksize = bh->b_size;

@@ -2102,7 +2110,8 @@ static int __block_commit_write(struct inode *inode, struct page *page,
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
}
- clear_buffer_new(bh);
+ if (buffer_new(bh))
+ clear_buffer_new(bh);

block_start = block_end;
bh = bh->b_this_page;
@@ -2155,7 +2164,8 @@ int block_write_end(struct file *file, struct address_space *mapping,
struct inode *inode = mapping->host;
unsigned start;

- start = pos & (PAGE_SIZE - 1);
+ page = compound_head(page);
+ start = pos & ~hpage_mask(page);

if (unlikely(copied < len)) {
/*