Factor out a helper that does filemap_write_and_wait_range for the range
covered by a read kiocb, or returns -EAGAIN if the kiocb is marked as
nowait and there would be pages to write.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Damien Le Moal <dlem...@kernel.org>
Reviewed-by: Hannes Reinecke <h...@suse.de>
Acked-by: Darrick J. Wong <djw...@kernel.org>
---
 block/fops.c            | 18 +++---------------
 include/linux/pagemap.h |  2 ++
 mm/filemap.c            | 30 ++++++++++++++++++------------
 3 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 58d0aebc7313a8..575171049c5d83 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -576,21 +576,9 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct 
iov_iter *to)
                goto reexpand; /* skip atime */
 
        if (iocb->ki_flags & IOCB_DIRECT) {
-               struct address_space *mapping = iocb->ki_filp->f_mapping;
-
-               if (iocb->ki_flags & IOCB_NOWAIT) {
-                       if (filemap_range_needs_writeback(mapping, pos,
-                                                         pos + count - 1)) {
-                               ret = -EAGAIN;
-                               goto reexpand;
-                       }
-               } else {
-                       ret = filemap_write_and_wait_range(mapping, pos,
-                                                          pos + count - 1);
-                       if (ret < 0)
-                               goto reexpand;
-               }
-
+               ret = kiocb_write_and_wait(iocb, count);
+               if (ret < 0)
+                       goto reexpand;
                file_accessed(iocb->ki_filp);
 
                ret = blkdev_direct_IO(iocb, to);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a56308a9d1a450..36fc2cea13ce20 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -30,6 +30,7 @@ static inline void invalidate_remote_inode(struct inode 
*inode)
 int invalidate_inode_pages2(struct address_space *mapping);
 int invalidate_inode_pages2_range(struct address_space *mapping,
                pgoff_t start, pgoff_t end);
+
 int write_inode_now(struct inode *, int sync);
 int filemap_fdatawrite(struct address_space *);
 int filemap_flush(struct address_space *);
@@ -54,6 +55,7 @@ int filemap_check_errors(struct address_space *mapping);
 void __filemap_set_wb_err(struct address_space *mapping, int err);
 int filemap_fdatawrite_wbc(struct address_space *mapping,
                           struct writeback_control *wbc);
+int kiocb_write_and_wait(struct kiocb *iocb, size_t count);
 
 static inline int filemap_write_and_wait(struct address_space *mapping)
 {
diff --git a/mm/filemap.c b/mm/filemap.c
index 15907af4a57ff5..5fcd5227f9cae2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2762,6 +2762,21 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter 
*iter,
 }
 EXPORT_SYMBOL_GPL(filemap_read);
 
+int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
+{
+       struct address_space *mapping = iocb->ki_filp->f_mapping;
+       loff_t pos = iocb->ki_pos;
+       loff_t end = pos + count - 1;
+
+       if (iocb->ki_flags & IOCB_NOWAIT) {
+               if (filemap_range_needs_writeback(mapping, pos, end))
+                       return -EAGAIN;
+               return 0;
+       }
+
+       return filemap_write_and_wait_range(mapping, pos, end);
+}
+
 /**
  * generic_file_read_iter - generic filesystem read routine
  * @iocb:      kernel I/O control block
@@ -2797,18 +2812,9 @@ generic_file_read_iter(struct kiocb *iocb, struct 
iov_iter *iter)
                struct address_space *mapping = file->f_mapping;
                struct inode *inode = mapping->host;
 
-               if (iocb->ki_flags & IOCB_NOWAIT) {
-                       if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
-                                               iocb->ki_pos + count - 1))
-                               return -EAGAIN;
-               } else {
-                       retval = filemap_write_and_wait_range(mapping,
-                                               iocb->ki_pos,
-                                               iocb->ki_pos + count - 1);
-                       if (retval < 0)
-                               return retval;
-               }
-
+               retval = kiocb_write_and_wait(iocb, count);
+               if (retval < 0)
+                       return retval;
                file_accessed(file);
 
                retval = mapping->a_ops->direct_IO(iocb, iter);
-- 
2.39.2



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