From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 9 Feb 2014 20:18:09 +0000 (-0500)
Subject: fix O_SYNC|O_APPEND syncing the wrong range on write()
X-Git-Tag: v3.14-rc2~2^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d311d79de305f1ada47cadd672e6ed1b28a949eb;p=pandora-kernel.git

fix O_SYNC|O_APPEND syncing the wrong range on write()

It actually goes back to 2004 ([PATCH] Concurrent O_SYNC write support)
when sync_page_range() had been introduced; generic_file_write{,v}() correctly
synced
	pos_after_write - written .. pos_after_write - 1
but generic_file_aio_write() synced
	pos_before_write .. pos_before_write + written - 1
instead.  Which is not the same thing with O_APPEND, obviously.
A couple of years later correct variant had been killed off when
everything switched to use of generic_file_aio_write().

All users of generic_file_aio_write() are affected, and the same bug
has been copied into other instances of ->aio_write().

The fix is trivial; the only subtle point is that generic_write_sync()
ought to be inlined to avoid calculations useless for the majority of
calls.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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