From 53bb540fd591f6fdd4cb5c9a785d9790ac33862d Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Tue, 26 Apr 2022 23:31:06 +0200 Subject: gfs2: Explain some direct I/O oddities Add some comments explaining the oddities of partial direct I/O reads and writes. Signed-off-by: Andreas Gruenbacher --- fs/gfs2/file.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'fs/gfs2/file.c') diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c index 2556ae1f92ea..f1d2f4d74b89 100644 --- a/fs/gfs2/file.c +++ b/fs/gfs2/file.c @@ -840,6 +840,7 @@ retry: pagefault_enable(); if (ret <= 0 && ret != -EFAULT) goto out_unlock; + /* No increment (+=) because iomap_dio_rw returns a cumulative value. */ if (ret > 0) read = ret; @@ -854,6 +855,7 @@ out_unlock: gfs2_glock_dq(gh); out_uninit: gfs2_holder_uninit(gh); + /* User space doesn't expect partial success. */ if (ret < 0) return ret; return read; @@ -906,6 +908,7 @@ retry: if (ret != -EFAULT) goto out_unlock; } + /* No increment (+=) because iomap_dio_rw returns a cumulative value. */ if (ret > 0) written = ret; @@ -920,6 +923,7 @@ out_unlock: gfs2_glock_dq(gh); out_uninit: gfs2_holder_uninit(gh); + /* User space doesn't expect partial success. */ if (ret < 0) return ret; return written; -- cgit