The recent generic_file_write() deadlock fix caused
generic_file_buffered_write() to loop inifinitely when presented with a
zero-length iovec segment. Fix.
Note that this fix deliberately avoids calling ->prepare_write(),
->commit_write() etc with a zero-length write. This is because I don't trust
all filesystems to get that right.
This is a cautious approach, for 2.6.17.x. For 2.6.18 we should just go ahead
and call ->prepare_write() and ->commit_write() with the zero length and fix
any broken filesystems. So I'll make that change once this code is stabilised
and backported into 2.6.17.x.
The reason for preferring to call ->prepare_write() and ->commit_write() with
the zero-length segment: a zero-length segment _should_ be sufficiently
uncommon that this is the correct way of handling it. We don't want to
optimise for poorly-written userspace at the expense of well-written
userspace.
Cc: "Vladimir V. Saveliev" <vs@namesys.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Greg KH <greg@kroah.com>
Cc: <stable@kernel.org>
Cc: walt <wa1ter@myrealbox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
81b0c87133