Merge tag 'printk-for-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux-2.6-microblaze.git] / fs / btrfs / inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 05e0c4a..0172f75 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7681,7 +7681,19 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) ||
            em->block_start == EXTENT_MAP_INLINE) {
                free_extent_map(em);
-               ret = -ENOTBLK;
+               /*
+                * If we are in a NOWAIT context, return -EAGAIN in order to
+                * fallback to buffered IO. This is not only because we can
+                * block with buffered IO (no support for NOWAIT semantics at
+                * the moment) but also to avoid returning short reads to user
+                * space - this happens if we were able to read some data from
+                * previous non-compressed extents and then when we fallback to
+                * buffered IO, at btrfs_file_read_iter() by calling
+                * filemap_read(), we fail to fault in pages for the read buffer,
+                * in which case filemap_read() returns a short read (the number
+                * of bytes previously read is > 0, so it does not return -EFAULT).
+                */
+               ret = (flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOTBLK;
                goto unlock_err;
        }