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SubjectRe: [f2fs-dev] [PATCH v2] f2fs: introduce F2FS_IOC_START_ATOMIC_REPLACE
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On 2022/9/20 9:40, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.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@google.com>
> ---
> v2: add undefined ioctl number reported by <lkp@intel.com>
> ---
> fs/f2fs/data.c | 3 +++
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/file.c | 12 ++++++++++--
> fs/f2fs/segment.c | 14 +++++++++++++-
> include/uapi/linux/f2fs.h | 1 +
> 5 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 6cd29a575105..d3d32db3a25d 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3438,6 +3438,9 @@ 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 539da7f12cfc..2c49da12d6d8 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -764,6 +764,7 @@ enum {
> FI_COMPRESS_RELEASED, /* compressed blocks were released */
> FI_ALIGNED_WRITE, /* enable aligned write */
> FI_COW_FILE, /* indicate COW file */
> + 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 4f9b80c41b1e..4abd9d2a55b3 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1982,7 +1982,7 @@ 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);
> @@ -2051,6 +2051,12 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>
> 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;
> + }

Hi Daeho,

isize should be updated after tagging inode as atomic_write one?
otherwise f2fs_mark_inode_dirty_sync() may update isize to inode page,
latter checkpoint may persist that change? IIUC...

Thanks,

> f2fs_i_size_write(fi->cow_inode, isize);
>
> spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> @@ -4080,7 +4086,9 @@ 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 143b7ea0fb8e..c524538a9013 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -263,14 +263,26 @@ 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;
> + }
> +
> list_del(&cur->list);
> kmem_cache_free(revoke_entry_slab, cur);
> }
> +
> + if (!revoke && truncate) {
> + f2fs_do_truncate_blocks(inode, start_index * PAGE_SIZE, false);
> + clear_inode_flag(inode, FI_ATOMIC_REPLACE);
> + }
> }
>
> 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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