On Fri, Aug 20, 2021 at 10:59:28AM +0300, Nikolay Borisov wrote:

On 18.08.21 г. 0:06, Omar Sandoval wrote:

quoted

From: Omar Sandoval <redacted>

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 <redacted>
---
 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;

 Missing 'if(!count) return 0' from original code ?

Good catch, thanks.