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Date:   Fri, 4 Jun 2021 16:51:58 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Chao Yu <yuchao0@huawei.com>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] f2fs: swap: remove dead codes
Message-ID: <YLq8nlrxfotXnerU@google.com>
References: <20210526062927.52629-1-yuchao0@huawei.com>
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 <YK74cyGYzWZCmZue@google.com>
 <21ec5a95-bdbc-358d-99c7-e75e91228039@huawei.com>
 <ce4d1663-4082-625f-4c3f-858bf03bbb26@kernel.org>
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On 06/04, Chao Yu wrote:
> 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

Yeah, we need to block the large page support unfortunately. :(

> 
> 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
> > > .
> > >