[PATCHv3 24/41] fs: make block_write_{begin,end}() be able to handle huge pages

Kirill A. Shutemov
2016-09-15T11:55:06Z

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 | 53 +++++++++++++++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 22 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 2739f5dae690..7f50e5a63670 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1870,21 +1870,21 @@ 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 (!PageUptodate(page)) {
+ 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;
@@ -1950,18 +1950,20 @@ 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;

+ 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);
@@ -2001,10 +2003,15 @@ int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
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;
}
}
@@ -2048,6 +2055,7 @@ 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;

@@ -2114,7 +2122,8 @@ 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)) {
/*