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Message-ID: <6e26eb7d-8b9e-5a91-b66f-a6f8cf1d53ce@kernel.org>
Date: Wed, 23 Nov 2022 23:23:27 +0800
From: Chao Yu <chao@...nel.org>
To: Daeho Jeong <daeho43@...il.com>, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Cc: Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v7] f2fs: introduce
F2FS_IOC_START_ATOMIC_REPLACE
On 2022/11/12 1:04, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@...gle.com>
>
> introduce a new ioctl to replace the whole content of a file atomically,
> which means it induces truncate and content update at the same time.
> We can start it with F2FS_IOC_START_ATOMIC_REPLACE and complete it with
> F2FS_IOC_COMMIT_ATOMIC_WRITE. Or abort it with
> F2FS_IOC_ABORT_ATOMIC_WRITE.
>
> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> ---
> v7: changed where to clear FI_ATOMIC_REPLACE
> fixed tentative race condition in f2fs_ioc_start_atomic_write()
> v3: move i_size change after setting atomic write flag
> v2: add undefined ioctl number reported by <lkp@...el.com>
> ---
> fs/f2fs/data.c | 3 +++
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/file.c | 21 +++++++++++++++------
> fs/f2fs/segment.c | 13 ++++++++++++-
> include/uapi/linux/f2fs.h | 1 +
> 5 files changed, 32 insertions(+), 7 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5f895ddcd64a..bce4dcc3ad78 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3457,6 +3457,9 @@ static int prepare_atomic_write_begin(struct f2fs_sb_info *sbi,
> else if (*blk_addr != NULL_ADDR)
> return 0;
>
> + if (is_inode_flag_set(inode, FI_ATOMIC_REPLACE))
> + goto reserve_block;
> +
> /* Look for the block in the original inode */
> err = __find_data_block(inode, index, &ori_blk_addr);
> if (err)
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e29f9adf60ca..d513ecd17550 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -765,6 +765,7 @@ enum {
> FI_ALIGNED_WRITE, /* enable aligned write */
> FI_COW_FILE, /* indicate COW file */
> FI_ATOMIC_COMMITTED, /* indicate atomic commit completed except disk sync */
> + FI_ATOMIC_REPLACE, /* indicate atomic replace */
> FI_MAX, /* max flag, never be used */
> };
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 7ce629c95f4a..f9a04f6d76cb 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1984,7 +1984,7 @@ static int f2fs_ioc_getversion(struct file *filp, unsigned long arg)
> return put_user(inode->i_generation, (int __user *)arg);
> }
>
> -static int f2fs_ioc_start_atomic_write(struct file *filp)
> +static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate)
> {
> struct inode *inode = file_inode(filp);
> struct user_namespace *mnt_userns = file_mnt_user_ns(filp);
> @@ -2053,15 +2053,22 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>
> f2fs_write_inode(inode, NULL);
>
> - isize = i_size_read(inode);
> - fi->original_i_size = isize;
> - f2fs_i_size_write(fi->cow_inode, isize);
> -
> stat_inc_atomic_inode(inode);
>
> set_inode_flag(inode, FI_ATOMIC_FILE);
> set_inode_flag(fi->cow_inode, FI_COW_FILE);
> clear_inode_flag(fi->cow_inode, FI_INLINE_DATA);
> +
> + isize = i_size_read(inode);
> + fi->original_i_size = isize;
> + if (truncate) {
> + set_inode_flag(inode, FI_ATOMIC_REPLACE);
> + truncate_inode_pages_final(inode->i_mapping);
> + f2fs_i_size_write(inode, 0);
> + isize = 0;
> + }
> + f2fs_i_size_write(fi->cow_inode, isize);
> +
> f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
>
> f2fs_update_time(sbi, REQ_TIME);
> @@ -4089,7 +4096,9 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> case FS_IOC_GETVERSION:
> return f2fs_ioc_getversion(filp, arg);
> case F2FS_IOC_START_ATOMIC_WRITE:
> - return f2fs_ioc_start_atomic_write(filp);
> + return f2fs_ioc_start_atomic_write(filp, false);
> + case F2FS_IOC_START_ATOMIC_REPLACE:
> + return f2fs_ioc_start_atomic_write(filp, true);
> case F2FS_IOC_COMMIT_ATOMIC_WRITE:
> return f2fs_ioc_commit_atomic_write(filp);
> case F2FS_IOC_ABORT_ATOMIC_WRITE:
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 9cbf88092c78..f2930fffbc7d 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -197,6 +197,7 @@ void f2fs_abort_atomic_write(struct inode *inode, bool clean)
> fi->cow_inode = NULL;
> release_atomic_write_cnt(inode);
> clear_inode_flag(inode, FI_ATOMIC_COMMITTED);
> + clear_inode_flag(inode, FI_ATOMIC_REPLACE);
> clear_inode_flag(inode, FI_ATOMIC_FILE);
> stat_dec_atomic_inode(inode);
>
> @@ -261,14 +262,24 @@ static void __complete_revoke_list(struct inode *inode, struct list_head *head,
> bool revoke)
> {
> struct revoke_entry *cur, *tmp;
> + pgoff_t start_index = 0;
> + bool truncate = is_inode_flag_set(inode, FI_ATOMIC_REPLACE);
>
> list_for_each_entry_safe(cur, tmp, head, list) {
> - if (revoke)
> + if (revoke) {
> __replace_atomic_write_block(inode, cur->index,
> cur->old_addr, NULL, true);
> + } else if (truncate) {
> + f2fs_truncate_hole(inode, start_index, cur->index);
> + start_index = cur->index + 1;
Do we try to truncate from page #0 to page #(index of last page in chain)?
If so, how about calling f2fs_truncate_hole(, 0, last_index) after the loop?
Thanks,
> + }
> +
> list_del(&cur->list);
> kmem_cache_free(revoke_entry_slab, cur);
> }
> +
> + if (!revoke && truncate)
> + f2fs_do_truncate_blocks(inode, start_index * PAGE_SIZE, false);
> }
>
> static int __f2fs_commit_atomic_write(struct inode *inode)
> diff --git a/include/uapi/linux/f2fs.h b/include/uapi/linux/f2fs.h
> index 3121d127d5aa..955d440be104 100644
> --- a/include/uapi/linux/f2fs.h
> +++ b/include/uapi/linux/f2fs.h
> @@ -42,6 +42,7 @@
> struct f2fs_comp_option)
> #define F2FS_IOC_DECOMPRESS_FILE _IO(F2FS_IOCTL_MAGIC, 23)
> #define F2FS_IOC_COMPRESS_FILE _IO(F2FS_IOCTL_MAGIC, 24)
> +#define F2FS_IOC_START_ATOMIC_REPLACE _IO(F2FS_IOCTL_MAGIC, 25)
>
> /*
> * should be same as XFS_IOC_GOINGDOWN.
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