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-rw-r--r--fs/btrfs/inode.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f0c97d25b4a0..ad250892028d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7694,6 +7694,20 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
bool unlock_extents = false;
/*
+ * We could potentially fault if we have a buffer > PAGE_SIZE, and if
+ * we're NOWAIT we may submit a bio for a partial range and return
+ * EIOCBQUEUED, which would result in an errant short read.
+ *
+ * The best way to handle this would be to allow for partial completions
+ * of iocb's, so we could submit the partial bio, return and fault in
+ * the rest of the pages, and then submit the io for the rest of the
+ * range. However we don't have that currently, so simply return
+ * -EAGAIN at this point so that the normal path is used.
+ */
+ if (!write && (flags & IOMAP_NOWAIT) && length > PAGE_SIZE)
+ return -EAGAIN;
+
+ /*
* Cap the size of reads to that usually seen in buffered I/O as we need
* to allocate a contiguous array for the checksums.
*/