On 2020/10/27 13:38, Daeho Jeong wrote:
From: Daeho Jeong <daehoje...@google.com>

Added a new F2FS_IOC_SET_COMPRESS_OPTION ioctl to change file
compression option of a file.

struct f2fs_comp_option {
     u8 algorithm;         => compression algorithm
                           => 0:lzo, 1:lz4, 2:zstd, 3:lzorle
     u8 log_cluster_size;  => log scale cluster size
                           => 2 ~ 8
};

struct f2fs_comp_option option;

option.algorithm = 1;
option.log_cluster_size = 7;

ioctl(fd, F2FS_IOC_SET_COMPRESS_OPTION, &option);

Signed-off-by: Daeho Jeong <daehoje...@google.com>
---

v4: changed commit message.
v3: changed the error number more specific.
     folded in fix for build breakage reported by kernel test robot
     <l...@intel.com> and Dan Carpenter <dan.carpen...@oracle.com>.
v2: added ioctl description.
---
  fs/f2fs/compress.c |  5 +++++
  fs/f2fs/f2fs.h     |  7 +++++++
  fs/f2fs/file.c     | 52 ++++++++++++++++++++++++++++++++++++++++++++++
  3 files changed, 64 insertions(+)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 7895186cc765..816d7adc914c 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -514,6 +514,11 @@ bool f2fs_is_compress_backend_ready(struct inode *inode)
        return f2fs_cops[F2FS_I(inode)->i_compress_algorithm];
  }
+bool f2fs_is_compress_algorithm_ready(unsigned char algorithm)
+{
+       return algorithm < COMPRESS_MAX && f2fs_cops[algorithm] != NULL;
+}
+
  static mempool_t *compress_page_pool;
  static int num_compress_pages = 512;
  module_param(num_compress_pages, uint, 0444);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a33c90cf979b..cc38afde6c04 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -435,6 +435,8 @@ static inline bool __has_cursum_space(struct f2fs_journal 
*journal,
                                                struct f2fs_sectrim_range)
  #define F2FS_IOC_GET_COMPRESS_OPTION  _IOR(F2FS_IOCTL_MAGIC, 21,      \
                                                struct f2fs_comp_option)
+#define F2FS_IOC_SET_COMPRESS_OPTION   _IOW(F2FS_IOCTL_MAGIC, 22,      \
+                                               struct f2fs_comp_option)
/*
   * should be same as XFS_IOC_GOINGDOWN.
@@ -3915,6 +3917,7 @@ bool f2fs_compress_write_end(struct inode *inode, void 
*fsdata,
  int f2fs_truncate_partial_cluster(struct inode *inode, u64 from, bool lock);
  void f2fs_compress_write_end_io(struct bio *bio, struct page *page);
  bool f2fs_is_compress_backend_ready(struct inode *inode);
+bool f2fs_is_compress_algorithm_ready(unsigned char algorithm);
  int f2fs_init_compress_mempool(void);
  void f2fs_destroy_compress_mempool(void);
  void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity);
@@ -3945,6 +3948,10 @@ static inline bool f2fs_is_compress_backend_ready(struct 
inode *inode)
        /* not support compression */
        return false;
  }
+static inline bool f2fs_is_compress_algorithm_ready(unsigned char algorithm)
+{
+       return false;
+}
  static inline struct page *f2fs_compress_control_page(struct page *page)
  {
        WARN_ON_ONCE(1);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 8922ab191a9d..8048b150e43b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3963,6 +3963,55 @@ static int f2fs_ioc_get_compress_option(struct file 
*filp, unsigned long arg)
        return 0;
  }
+static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
+{
+       struct inode *inode = file_inode(filp);
+       struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+       struct f2fs_comp_option option;
+       int ret = 0;
+
+       if (!f2fs_sb_has_compression(sbi))
+               return -EOPNOTSUPP;
+
+       if (!(filp->f_mode & FMODE_WRITE))
+               return -EBADF;
+
+       if (copy_from_user(&option, (struct f2fs_comp_option __user *)arg,
+                               sizeof(option)))
+               return -EFAULT;
+
+       if (!f2fs_compressed_file(inode) ||
+                       option.log_cluster_size < MIN_COMPRESS_LOG_SIZE ||
+                       option.log_cluster_size > MAX_COMPRESS_LOG_SIZE)
+               return -EINVAL;
+
+       if (!f2fs_is_compress_algorithm_ready(option.algorithm))
+               return -ENOPKG;

As we allow to mount image with different kernel which supports different 
compress
algorithms, so I guess we can support to change algorithm to one other which 
current
kernel doesn't support, since we have add f2fs_is_compress_backend_ready() in 
all
foreground operations to disallow user to operate such inode's data.

IMO, just add to print one warnning message is fine.

Thanks,

+
+       file_start_write(filp);
+       inode_lock(inode);
+
+       if (f2fs_is_mmap_file(inode) || get_dirty_pages(inode)) {
+               ret = -EBUSY;
+               goto out;
+       }
+
+       if (inode->i_size != 0) {
+               ret = -EFBIG;
+               goto out;
+       }
+
+       F2FS_I(inode)->i_compress_algorithm = option.algorithm;
+       F2FS_I(inode)->i_log_cluster_size = option.log_cluster_size;
+       F2FS_I(inode)->i_cluster_size = 1 << option.log_cluster_size;
+       f2fs_mark_inode_dirty_sync(inode, true);
+out:
+       inode_unlock(inode);
+       file_end_write(filp);
+
+       return ret;
+}
+
  long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  {
        if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp)))))
@@ -4053,6 +4102,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, 
unsigned long arg)
                return f2fs_sec_trim_file(filp, arg);
        case F2FS_IOC_GET_COMPRESS_OPTION:
                return f2fs_ioc_get_compress_option(filp, arg);
+       case F2FS_IOC_SET_COMPRESS_OPTION:
+               return f2fs_ioc_set_compress_option(filp, arg);
        default:
                return -ENOTTY;
        }
@@ -4224,6 +4275,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int 
cmd, unsigned long arg)
        case F2FS_IOC_RESERVE_COMPRESS_BLOCKS:
        case F2FS_IOC_SEC_TRIM_FILE:
        case F2FS_IOC_GET_COMPRESS_OPTION:
+       case F2FS_IOC_SET_COMPRESS_OPTION:
                break;
        default:
                return -ENOIOCTLCMD;

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