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Subject[PATCH] f2fs: fix to add swap extent correctly
Date
As Youling reported in mailing list:

https://www.linuxquestions.org/questions/linux-newbie-8/the-file-system-f2fs-is-broken-4175666043/

https://www.linux.org/threads/the-file-system-f2fs-is-broken.26490/

There is a test case can corrupt f2fs image:
- dd if=/dev/zero of=/swapfile bs=1M count=4096
- chmod 600 /swapfile
- mkswap /swapfile
- swapon --discard /swapfile

The root cause is f2fs_swap_activate() intends to return zero value
to setup_swap_extents() to enable SWP_FS mode (swap file goes through
fs), in this flow, setup_swap_extents() setups swap extent with wrong
block address range, result in discard_swap() erasing incorrect address.

Because f2fs_swap_activate() has pinned swapfile, its data block
address will not change, it's safe to let swap to handle IO through
raw device, so we can get rid of SWAP_FS mode and initial swap extents
inside f2fs_swap_activate(), by this way, later discard_swap() can trim
in right address range.

Fixes: 4969c06a0d83 ("f2fs: support swap file w/ DIO")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
fs/f2fs/data.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 19cd03450066..ee4d3d284379 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3608,7 +3608,8 @@ int f2fs_migrate_page(struct address_space *mapping,

#ifdef CONFIG_SWAP
/* Copied from generic_swapfile_activate() to check any holes */
-static int check_swap_activate(struct file *swap_file, unsigned int max)
+static int check_swap_activate(struct swap_info_struct *sis,
+ struct file *swap_file, sector_t *span)
{
struct address_space *mapping = swap_file->f_mapping;
struct inode *inode = mapping->host;
@@ -3619,6 +3620,8 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
sector_t last_block;
sector_t lowest_block = -1;
sector_t highest_block = 0;
+ int nr_extents = 0;
+ int ret;

blkbits = inode->i_blkbits;
blocks_per_page = PAGE_SIZE >> blkbits;
@@ -3630,7 +3633,8 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
probe_block = 0;
page_no = 0;
last_block = i_size_read(inode) >> blkbits;
- while ((probe_block + blocks_per_page) <= last_block && page_no < max) {
+ while ((probe_block + blocks_per_page) <= last_block &&
+ page_no < sis->max) {
unsigned block_in_page;
sector_t first_block;

@@ -3670,13 +3674,27 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
highest_block = first_block;
}

+ /*
+ * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
+ */
+ ret = add_swap_extent(sis, page_no, 1, first_block);
+ if (ret < 0)
+ goto out;
+ nr_extents += ret;
page_no++;
probe_block += blocks_per_page;
reprobe:
continue;
}
- return 0;
-
+ ret = nr_extents;
+ *span = 1 + highest_block - lowest_block;
+ if (page_no == 0)
+ page_no = 1; /* force Empty message */
+ sis->max = page_no;
+ sis->pages = page_no - 1;
+ sis->highest_bit = page_no - 1;
+out:
+ return ret;
bad_bmap:
pr_err("swapon: swapfile has holes\n");
return -EINVAL;
@@ -3701,14 +3719,14 @@ static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
if (f2fs_disable_compressed_file(inode))
return -EINVAL;

- ret = check_swap_activate(file, sis->max);
- if (ret)
+ ret = check_swap_activate(sis, file, span);
+ if (ret < 0)
return ret;

set_inode_flag(inode, FI_PIN_FILE);
f2fs_precache_extents(inode);
f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
- return 0;
+ return ret;
}

static void f2fs_swap_deactivate(struct file *file)
--
2.18.0.rc1
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