Fsync is really an inode operation (AFAICS) so a doing it on a O_RDONLY
file descriptor should flush any data written through an O_WRONLY file
descriptor for example.
To make this work correctly in case the file is copied up after being
opened for read intercept the fsync fop, similarly to read_iter and mmap.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/overlayfs/inode.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 210838f97777..d861aa7462c5 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -412,6 +412,24 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
return file->f_op->mmap(file, vma);
}
+static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+ int ret;
+
+ if (likely(ovl_file_is_lower(file))) {
+ return OVL_CALL_REAL_FOP(file,
+ fsync(file, start, end, datasync));
+ }
+ file = filp_clone_open(file);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ ret = vfs_fsync_range(file, start, end, datasync);
+ fput(file);
+
+ return ret;
+}
+
static struct ovl_fops *ovl_fops_find(const struct file_operations *orig)
{
struct ovl_fops *ofop;
@@ -455,9 +473,8 @@ static struct ovl_fops *ovl_fops_get(struct file *file)
ofop->fops.read_iter = ovl_read_iter;
if (orig->mmap)
ofop->fops.mmap = ovl_mmap;
-
- /* These will need to be intercepted: */
- ofop->fops.fsync = orig->fsync;
+ if (orig->fsync)
+ ofop->fops.fsync = ovl_fsync;
/*
* These should be intercepted, but they are very unlikely to be
--
2.5.5
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