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Subject: Re: [PATCH 1/2] f2fs: swap: remove dead codes
To:     Chao Yu <yuchao0@huawei.com>, Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
References: <20210526062927.52629-1-yuchao0@huawei.com>
 <YK5NXdyjgB6EFY5Q@google.com>
 <e4c1df88-f1f4-99e0-6f83-fa0f3110d737@kernel.org>
 <YK74cyGYzWZCmZue@google.com>
 <21ec5a95-bdbc-358d-99c7-e75e91228039@huawei.com>
From:   Chao Yu <chao@kernel.org>
Message-ID: <ce4d1663-4082-625f-4c3f-858bf03bbb26@kernel.org>
Date:   Fri, 4 Jun 2021 19:12:27 +0800
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On 2021/5/27 10:12, Chao Yu wrote:
> On 2021/5/27 9:40, Jaegeuk Kim wrote:
>> On 05/26, Chao Yu wrote:
>>> On 2021/5/26 21:30, Jaegeuk Kim wrote:
>>>> On 05/26, Chao Yu wrote:
>>>>> After commit af4b6b8edf6a ("f2fs: introduce check_swap_activate_fast()"),
>>>>> we will never run into original logic of check_swap_activate() before
>>>>> f2fs supports non 4k-sized page, so let's delete those dead codes.
>>>>
>>>> Why not keeping this for large page support in future maybe?
>>>
>>> Well, if so, at that time, it would be better to refactor
>>> check_swap_activate_fast() implementation based on f2fs_map_block() rather
>>> than refactoring check_swap_activate() implementation based on low efficient
>>> bmap()?
>>
>> Let's first check whether we support large page. Have you quickly tested it?
>> If we support it now and current flow is just inefficient, I'd say keeping but
>> refactoring it later.
> 
> Let me check this, but I guess it missed to handle large page in lots of flows,
> not sure where we may panic at... :(

I've checked f2fs behavior on 64kb page size in arm64 vm,
- 'ls -ls' will cause f2fs printing "invalid namelen(0), ino:%u, run fsck
to fix." each time.
- after touch a file and umount, fsck reports that image is corrupted.

F2FS uses PAGE_SIZE and F2FS_BLKSIZE directly in a lot of places, I doubt
most of places may not consider large page size condition.

So, thoughts? I guess we have to admit we do not support 64KB page right
now... :P

Thanks,

> 
> Thanks,
> 
>>
>>>
>>> Thanks,
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>> ---
>>>>> ?? fs/f2fs/data.c | 171 +------------------------------------------------
>>>>> ?? 1 file changed, 3 insertions(+), 168 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>> index 3058c7e28b11..9c23fde93b76 100644
>>>>> --- a/fs/f2fs/data.c
>>>>> +++ b/fs/f2fs/data.c
>>>>> @@ -3830,67 +3830,7 @@ int f2fs_migrate_page(struct address_space *mapping,
>>>>> ?? #endif
>>>>> ?? #ifdef CONFIG_SWAP
>>>>> -static int f2fs_is_file_aligned(struct inode *inode)
>>>>> -{
>>>>> -??? struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>> -??? block_t main_blkaddr = SM_I(sbi)->main_blkaddr;
>>>>> -??? block_t cur_lblock;
>>>>> -??? block_t last_lblock;
>>>>> -??? block_t pblock;
>>>>> -??? unsigned long nr_pblocks;
>>>>> -??? unsigned int blocks_per_sec = BLKS_PER_SEC(sbi);
>>>>> -??? unsigned int not_aligned = 0;
>>>>> -??? int ret = 0;
>>>>> -
>>>>> -??? cur_lblock = 0;
>>>>> -??? last_lblock = bytes_to_blks(inode, i_size_read(inode));
>>>>> -
>>>>> -??? while (cur_lblock < last_lblock) {
>>>>> -??????? struct f2fs_map_blocks map;
>>>>> -
>>>>> -??????? memset(&map, 0, sizeof(map));
>>>>> -??????? map.m_lblk = cur_lblock;
>>>>> -??????? map.m_len = last_lblock - cur_lblock;
>>>>> -??????? map.m_next_pgofs = NULL;
>>>>> -??????? map.m_next_extent = NULL;
>>>>> -??????? map.m_seg_type = NO_CHECK_TYPE;
>>>>> -??????? map.m_may_create = false;
>>>>> -
>>>>> -??????? ret = f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_FIEMAP);
>>>>> -??????? if (ret)
>>>>> -??????????? goto out;
>>>>> -
>>>>> -??????? /* hole */
>>>>> -??????? if (!(map.m_flags & F2FS_MAP_FLAGS)) {
>>>>> -??????????? f2fs_err(sbi, "Swapfile has holes\n");
>>>>> -??????????? ret = -ENOENT;
>>>>> -??????????? goto out;
>>>>> -??????? }
>>>>> -
>>>>> -??????? pblock = map.m_pblk;
>>>>> -??????? nr_pblocks = map.m_len;
>>>>> -
>>>>> -??????? if ((pblock - main_blkaddr) & (blocks_per_sec - 1) ||
>>>>> -??????????? nr_pblocks & (blocks_per_sec - 1)) {
>>>>> -??????????? if (f2fs_is_pinned_file(inode)) {
>>>>> -??????????????? f2fs_err(sbi, "Swapfile does not align to section");
>>>>> -??????????????? ret = -EINVAL;
>>>>> -??????????????? goto out;
>>>>> -??????????? }
>>>>> -??????????? not_aligned++;
>>>>> -??????? }
>>>>> -
>>>>> -??????? cur_lblock += nr_pblocks;
>>>>> -??? }
>>>>> -??? if (not_aligned)
>>>>> -??????? f2fs_warn(sbi, "Swapfile (%u) is not align to section: \n"
>>>>> -??????????? "\t1) creat(), 2) ioctl(F2FS_IOC_SET_PIN_FILE), 3) fallocate()",
>>>>> -??????????? not_aligned);
>>>>> -out:
>>>>> -??? return ret;
>>>>> -}
>>>>> -
>>>>> -static int check_swap_activate_fast(struct swap_info_struct *sis,
>>>>> +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;
>>>>> @@ -3907,6 +3847,8 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>>>>> ?????? unsigned int not_aligned = 0;
>>>>> ?????? int ret = 0;
>>>>> +??? f2fs_bug_on(sbi, PAGE_SIZE != F2FS_BLKSIZE);
>>>>> +
>>>>> ?????? /*
>>>>> ??????? * Map all the blocks into the extent list.? This code doesn't try
>>>>> ??????? * to be very smart.
>>>>> @@ -3986,113 +3928,6 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>>>>> ?????? return ret;
>>>>> ?? }
>>>>> -/* Copied from generic_swapfile_activate() to check any holes */
>>>>> -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;
>>>>> -??? struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>> -??? unsigned blocks_per_page;
>>>>> -??? unsigned long page_no;
>>>>> -??? sector_t probe_block;
>>>>> -??? sector_t last_block;
>>>>> -??? sector_t lowest_block = -1;
>>>>> -??? sector_t highest_block = 0;
>>>>> -??? int nr_extents = 0;
>>>>> -??? int ret = 0;
>>>>> -
>>>>> -??? if (PAGE_SIZE == F2FS_BLKSIZE)
>>>>> -??????? return check_swap_activate_fast(sis, swap_file, span);
>>>>> -
>>>>> -??? ret = f2fs_is_file_aligned(inode);
>>>>> -??? if (ret)
>>>>> -??????? goto out;
>>>>> -
>>>>> -??? blocks_per_page = bytes_to_blks(inode, PAGE_SIZE);
>>>>> -
>>>>> -??? /*
>>>>> -???? * Map all the blocks into the extent list.? This code doesn't try
>>>>> -???? * to be very smart.
>>>>> -???? */
>>>>> -??? probe_block = 0;
>>>>> -??? page_no = 0;
>>>>> -??? last_block = bytes_to_blks(inode, i_size_read(inode));
>>>>> -??? while ((probe_block + blocks_per_page) <= last_block &&
>>>>> -??????????? page_no < sis->max) {
>>>>> -??????? unsigned block_in_page;
>>>>> -??????? sector_t first_block;
>>>>> -??????? sector_t block = 0;
>>>>> -
>>>>> -??????? cond_resched();
>>>>> -
>>>>> -??????? block = probe_block;
>>>>> -??????? ret = bmap(inode, &block);
>>>>> -??????? if (ret)
>>>>> -??????????? goto out;
>>>>> -??????? if (!block)
>>>>> -??????????? goto bad_bmap;
>>>>> -??????? first_block = block;
>>>>> -
>>>>> -??????? /*
>>>>> -???????? * It must be PAGE_SIZE aligned on-disk
>>>>> -???????? */
>>>>> -??????? if (first_block & (blocks_per_page - 1)) {
>>>>> -??????????? probe_block++;
>>>>> -??????????? goto reprobe;
>>>>> -??????? }
>>>>> -
>>>>> -??????? for (block_in_page = 1; block_in_page < blocks_per_page;
>>>>> -??????????????????? block_in_page++) {
>>>>> -
>>>>> -??????????? block = probe_block + block_in_page;
>>>>> -??????????? ret = bmap(inode, &block);
>>>>> -??????????? if (ret)
>>>>> -??????????????? goto out;
>>>>> -??????????? if (!block)
>>>>> -??????????????? goto bad_bmap;
>>>>> -
>>>>> -??????????? if (block != first_block + block_in_page) {
>>>>> -??????????????? /* Discontiguity */
>>>>> -??????????????? probe_block++;
>>>>> -??????????????? goto reprobe;
>>>>> -??????????? }
>>>>> -??????? }
>>>>> -
>>>>> -??????? first_block >>= (PAGE_SHIFT - inode->i_blkbits);
>>>>> -??????? if (page_no) {??? /* exclude the header page */
>>>>> -??????????? if (first_block < lowest_block)
>>>>> -??????????????? lowest_block = first_block;
>>>>> -??????????? if (first_block > highest_block)
>>>>> -??????????????? 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;
>>>>> -??? }
>>>>> -??? 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:
>>>>> -??? f2fs_err(sbi, "Swapfile has holes\n");
>>>>> -??? return -EINVAL;
>>>>> -}
>>>>> -
>>>>> ?? static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
>>>>> ?????????????????? sector_t *span)
>>>>> ?? {
>>>>> -- 
>>>>> 2.29.2
>> .
>>