[PATCH v10 02/14] fs: export variant of generic_write_checks without iov_iter

Omar Sandoval
2021-08-17T21:07:20Z

From: Omar Sandoval <osandov@fb.com>

Encoded I/O in Btrfs needs to check a write with a given logical size
without an iov_iter that matches that size (because the iov_iter we have
is for the compressed data). So, factor out the parts of
generic_write_check() that expect an iov_iter into a new
__generic_write_checks() function and export that.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/read_write.c | 40 ++++++++++++++++++++++------------------
include/linux/fs.h | 1 +
2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 0029ff2b0ca8..3bddd5ee7f64 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1633,6 +1633,26 @@ int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
return 0;
}

+/* Like generic_write_checks(), but takes size of write instead of iter. */
+int __generic_write_checks(struct kiocb *iocb, loff_t *count)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+
+ /* FIXME: this is for backwards compatibility with 2.4 */
+ if (iocb->ki_flags & IOCB_APPEND)
+ iocb->ki_pos = i_size_read(inode);
+
+ if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
+ return -EINVAL;
+
+ return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count);
+}
+EXPORT_SYMBOL(__generic_write_checks);
+
/*
* Performs necessary checks before doing a write
*
@@ -1642,26 +1662,10 @@ int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
*/
ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
- struct file *file = iocb->ki_filp;
- struct inode *inode = file->f_mapping->host;
- loff_t count;
+ loff_t count = iov_iter_count(from);
int ret;

- if (IS_SWAPFILE(inode))
- return -ETXTBSY;
-
- if (!iov_iter_count(from))
- return 0;
-
- /* FIXME: this is for backwards compatibility with 2.4 */
- if (iocb->ki_flags & IOCB_APPEND)
- iocb->ki_pos = i_size_read(inode);
-
- if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
- return -EINVAL;
-
- count = iov_iter_count(from);
- ret = generic_write_check_limits(file, iocb->ki_pos, &count);
+ ret = __generic_write_checks(iocb, &count);
if (ret)
return ret;

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0de4d75339b9..b206814da181 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3227,6 +3227,7 @@ extern int sb_min_blocksize(struct super_block *, int);
extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
+extern int __generic_write_checks(struct kiocb *iocb, loff_t *count);
extern int generic_write_check_limits(struct file *file, loff_t pos,
loff_t *count);
extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);
--
2.32.0