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swap: fix swapfile read/write offset 

We're not factoring in the start of the file for where to write and
read the swapfile, which leads to very unfortunate side effects of
writing where we should not be...

Fixes: 48d15436fd ("mm: remove get_swap_bio")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-03-02 14:53:21 -07:00
parent f5f4fc4649
commit caf6912f3f
3 changed files with 14 additions and 5 deletions
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1
include/linux/swap.h
View File

@ -485,6 +485,7 @@ struct backing_dev_info;
extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
extern void exit_swap_address_space(unsigned int type);
extern struct swap_info_struct *get_swap_device(swp_entry_t entry);
sector_t swap_page_sector(struct page *page);
static inline void put_swap_device(struct swap_info_struct *si)
{

5
mm/page_io.c
View File

@ -254,11 +254,6 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
return ret;
}
static sector_t swap_page_sector(struct page *page)
{
return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
}
static inline void count_swpout_vm_event(struct page *page)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

13
mm/swapfile.c
View File

@ -219,6 +219,19 @@ offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
BUG();
}
sector_t swap_page_sector(struct page *page)
{
struct swap_info_struct *sis = page_swap_info(page);
struct swap_extent *se;
sector_t sector;
pgoff_t offset;
offset = __page_file_index(page);
se = offset_to_swap_extent(sis, offset);
sector = se->start_block + (offset - se->start_page);
return sector << (PAGE_SHIFT - 9);
}
/*
* swap allocation tell device that a cluster of swap can now be discarded,
* to allow the swap device to optimize its wear-levelling.