How libcufile Check for O_DIRECT ( DIO) Flag

Infrastructure & Networking DOCA Storage
1

I am trying to make our device work with Libcufile , basically we want our device dma which has control of data trafer to its huge volatile memory to be used by GPu using GDS. its failing at
cufio_core:1259 cuFile DIO status for file descriptor 51 DirectIO not supported

How does libcufile check this Flag ?

2

To there is failure here… cuFileHandleRegister → 5008

3

On Linux, the canonical way to check whether a file descriptor was opened with O_DIRECT is:

  • fcntl(fd, F_GETFL) to retrieve the open flags, then

  • test the returned flags with & O_DIRECT

Conceptually:

Shell

int flags = fcntl(fd, F_GETFL);

if (flags < 0) { /* error */ }

bool has_odirect = (flags & O_DIRECT) != 0;

``

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That’s almost certainly the first “cheap” check libcufile performs, because it’s quick and doesn’t require any filesystem probing.

Important nuance: O_DIRECT is an open-time flag. If your application (or a library layer) opens the fd without O_DIRECT, libcufile cannot “add it later” just by checking; it will reject for DIO.