fs: export variant of generic_write_checks without iov_iter

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.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/read_write.c b/fs/read_write.c
index 4d60146..dc50001 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1618,24 +1618,16 @@ 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 */
@@ -1645,8 +1637,23 @@ 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 0ebfc25..27746a3 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3130,6 +3130,7 @@ 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 *);
+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);