FUSE currently disallows O_DIRECT flag in open(). It is tricky dealing with
setting/unsetting of O_DIRECT flag on an open file. There are applications
(primarily VMs and databases) which open files with O_DIRECT flag. These
applications do not work on FUSE due to this limitation.
The approach with this patch is to permit opens with O_DIRECT, but instead
disable setting/unsetting of the O_DIRECT flag no matter how the file was
opened. This limitation is for more practical than disallowing O_DIRECT
altogether.
Signed-off-by: Anand Avati <avati@xxxxxxxxxxx>
---
fs/fuse/file.c | 36 ++++++++++++++++++++++++++++++++----
1 files changed, 32 insertions(+), 4 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 82a6646..355c30f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -154,6 +154,27 @@ int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
return err;
}
+ if (file->f_flags & O_DIRECT) {
+ if (!(outarg.open_flags & FOPEN_DIRECT_IO)) {
+ /* filesystem process did not acknowledge the O_DIRECT
+ flag with FOPEN_DIRECT_IO bit in ourarg. Hence
+ we fail the open().
+
+ Notify the filesystem process about the failed
+ open with fuse_sync_release right here itself as
+ file->private_data is not yet set up for release
+ notification.
+ */
+ fuse_sync_release(ff, file->f_flags);
+ return -EINVAL;
+ }
+
+ /* make VFS believe we don't support O_DIRECT till we
+ implement a_ops->direct_IO
+ */
+ file->f_flags &= ~O_DIRECT;
+ }
+
if (isdir)
outarg.open_flags &= ~FOPEN_DIRECT_IO;
@@ -193,10 +214,6 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
struct fuse_conn *fc = get_fuse_conn(inode);
int err;
- /* VFS checks this, but only _after_ ->open() */
- if (file->f_flags & O_DIRECT)
- return -EINVAL;
-
err = generic_file_open(inode, file);
if (err)
return err;
@@ -2132,6 +2149,15 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc,
return 0;
}
+
+static int fuse_check_flags(struct file *filp, int flags)
+{
+ if ((filp->f_flags ^ flags) & O_DIRECT)
+ return -EINVAL;
+ return 0;
+}
+
+
static const struct file_operations fuse_file_operations = {
.llseek = fuse_file_llseek,
.read = do_sync_read,
@@ -2149,6 +2175,7 @@ static const struct file_operations fuse_file_operations = {
.unlocked_ioctl = fuse_file_ioctl,
.compat_ioctl = fuse_file_compat_ioctl,
.poll = fuse_file_poll,
+ .check_flags = fuse_check_flags,
};
static const struct file_operations fuse_direct_io_file_operations = {
@@ -2165,6 +2192,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
.unlocked_ioctl = fuse_file_ioctl,
.compat_ioctl = fuse_file_compat_ioctl,
.poll = fuse_file_poll,
+ .check_flags = fuse_check_flags,
/* no splice_read */
};
--
1.7.4.4
--
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