[Bug 218850] Unexpected failure when write to a file with two file descriptor

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218850

Theodore Tso (tytso@mit.edu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tytso@mit.edu
         Resolution|---                         |INVALID

--- Comment #3 from Theodore Tso (tytso@mit.edu) ---
Hint:   check the return value of all system calls.   In particular, check to
see what the read(fd_b, buf_4, 73728) returns.    Check to see what the size of
the file is after write(fd_a, buf_15, 9900), and then reflect on what happens
if the read ends up hitting the end of file marker, and what the offset of fd_b
is after the short read when hitting EOF.

Finally, read the documentation for the O_DIRECT flag in the NOTES section of
the open man page[1], and understand what the requirements are for O_DIRECT
writes, in particular about the alignment requirements are of the starting
offset when performing an O_DIRECT write (or O_DIRECT) read.   Then also check
on the errno return (for example replace the printf("write failure\n") with
perror("write").

[1] https://man7.org/linux/man-pages/man2/open.2.html

In any case, this is not a bug, and this is not a good place for you to be
asking for instruction in basic Unix system call programming.

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