From: Daeho Jeong <[email protected]>

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 <[email protected]>
---
 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 |  2 ++
 5 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 6cd29a575105..eef798b3e941 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_TRUNCATED))
+               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..79e7bed009bc 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_TRUNCATED,    /* indicate truncated atomic write */
        FI_MAX,                 /* max flag, never be used */
 };
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 4f9b80c41b1e..905810c62d47 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_TRUNCATED);
+               truncate_inode_pages_final(inode->i_mapping);
+               f2fs_i_size_write(inode, 0);
+               isize = 0;
+       }
        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..18aeec957ec9 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_TRUNCATED);
 
        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_TRUNCATED);
+       }
 }
 
 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..224d98731f22 100644
--- a/include/uapi/linux/f2fs.h
+++ b/include/uapi/linux/f2fs.h
@@ -42,6 +42,8 @@
                                                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_TRUNC_ATOMIC_WRITE                              \
+                                       _IO(F2FS_IOCTL_MAGIC, 25)
 
 /*
  * should be same as XFS_IOC_GOINGDOWN.
-- 
2.37.3.968.ga6b4b080e4-goog



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