tree 7382ea8e4bbda6ddf8d6f29f708aa531e262cd36
parent e2cd68f7cd07cc898581bd736ebdd6f2c2323c2e
author Linus Torvalds <torvalds@woody.linux-foundation.org> 1191269848 -0700
committer Linus Torvalds <torvalds@woody.linux-foundation.org> 1191269848 -0700

Fix possible splice() mmap_sem deadlock

Nick Piggin points out that splice isn't being good about the mmap
semaphore: while two readers can nest inside each others, it does leave
a possible deadlock if a writer (ie a new mmap()) comes in during that
nesting.

Original "just move the locking" patch by Nick, replaced by one by me
based on an optimistic pagefault_disable().  And then Jens tested and
updated that patch.

Reported-by: Nick Piggin <npiggin@suse.de>
Tested-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>