pty: don't limit the writes to 'pty_space()' inside 'pty_write()'
authorLinus Torvalds <torvalds@linux-foundation.org>
Sat, 5 Sep 2009 20:27:10 +0000 (13:27 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 5 Sep 2009 20:27:10 +0000 (13:27 -0700)
commitac89a9174decf343de049a06fad75681f71890eb
treec2fa9e7deef47b2cbc6bf4523e068a0265b105ac
parent37f81fa1f63ad38e16125526bb2769ae0ea8d332
pty: don't limit the writes to 'pty_space()' inside 'pty_write()'

The whole write-room thing is something that is up to the _caller_ to
worry about, not the pty layer itself.  The total buffer space will
still be limited by the buffering routines themselves, so there is no
advantage or need in having pty_write() artificially limit the size
somehow.

And what happened was that the caller (the n_tty line discipline, in
this case) may have verified that there is room for 2 bytes to be
written (for NL -> CRNL expansion), and it used to then do those writes
as two single-byte writes.  And if the first byte written (CR) then
caused a new tty buffer to be allocated, pty_space() may have returned
zero when trying to write the second byte (LF), and then incorrectly
failed the write - leading to a lost newline character.

This should finally fix

http://bugzilla.kernel.org/show_bug.cgi?id=14015

Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/char/pty.c