[PATCH v11 02/14] fs: export variant of generic_write_checks without iov_iter

Omar Sandoval
2021-09-01T17:01:32Z

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 don't need an iov_iter into a new
generic_write_checks_count() function and export that.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/read_write.c | 33 ++++++++++++++++++++-------------
include/linux/fs.h | 1 +
2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 0029ff2b0ca8..46b3dcff3b24 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1633,24 +1633,16 @@ int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
return 0;
}

-/*
- * Performs necessary checks before doing a write
- *
- * Can adjust writing position or amount of bytes to write.
- * Returns appropriate error code that caller should return or
- * zero in case that write should be allowed.
- */
-ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
+/* Like generic_write_checks(), but takes size of write instead of iter. */
+int generic_write_checks_count(struct kiocb *iocb, loff_t *count)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
- loff_t count;
- int ret;

if (IS_SWAPFILE(inode))
return -ETXTBSY;

- if (!iov_iter_count(from))
+ if (!*count)
return 0;

/* FIXME: this is for backwards compatibility with 2.4 */
@@ -1660,8 +1652,23 @@ ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
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);
+ return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count);
+}
+EXPORT_SYMBOL(generic_write_checks_count);
+
+/*
+ * Performs necessary checks before doing a write
+ *
+ * Can adjust writing position or amount of bytes to write.
+ * Returns appropriate error code that caller should return or
+ * zero in case that write should be allowed.
+ */
+ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
+{
+ loff_t count = iov_iter_count(from);
+ int ret;
+
+ ret = generic_write_checks_count(iocb, &count);
if (ret)
return ret;

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0de4d75339b9..3a2ff5306236 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_count(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);
--
2.33.0