If flags includes COPY_FILE_RANGE_FILESIZE then the length
copied is the length of the file. off_in and off_out are
ignored. len must be 0 or the file size.
This implementation saves a call to stat() in the common case
of copying files. It does not fix any race conditions, but that
is possible in the future with this interface.
EAGAIN: If COPY_FILE_RANGE_FILESIZE was passed and len is not 0
or the file size.
Signed-off-by: Shawn Landden <shawn@xxxxxxx>
CC: <linux-api@xxxxxxxxxxxxxxx>
---
fs/read_write.c | 14 +++++++++++++-
include/uapi/linux/stat.h | 4 ++++
2 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 61b43ad7608e..6d06361f0856 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1557,7 +1557,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
struct inode *inode_out = file_inode(file_out);
ssize_t ret;
- if (flags != 0)
+ if ((flags & ~COPY_FILE_RANGE_FILESIZE) != 0)
return -EINVAL;
if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
@@ -1565,6 +1565,18 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
return -EINVAL;
+ if (flags & COPY_FILE_RANGE_FILESIZE) {
+ struct kstat stat;
+ int error;
+ error = vfs_getattr(&file_in->f_path, &stat,
+ STATX_SIZE, 0);
+ if (error < 0)
+ return error;
+ if (!(len == 0 || len == stat.size))
+ return -EAGAIN;
+ len = stat.size;
+ }
+
ret = rw_verify_area(READ, file_in, &pos_in, len);
if (unlikely(ret))
return ret;
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 7b35e98d3c58..1075aa4666ef 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -170,5 +170,9 @@ struct statx {
#define STATX_ATTR_AUTOMOUNT 0x00001000 /* Dir: Automount trigger */
+/*
+ * Flags for copy_file_range()
+ */
+#define COPY_FILE_RANGE_FILESIZE 0x00000001 /* Copy the full length of the input file */
#endif /* _UAPI_LINUX_STAT_H */
--
2.20.1
