From 81b0c8713385ce1b1b9058e916edcf9561ad76d6 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Thu, 29 Jun 2006 02:24:26 -0700 Subject: [PATCH] generic_file_buffered_write(): handle zero-length iovec segments 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" Cc: Neil Brown Cc: Martin Schwidefsky Cc: Chris Wright Cc: Greg KH Cc: Cc: walt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/filemap.h') diff --git a/mm/filemap.h b/mm/filemap.h index 536979fb4ba7..3f2a343c6015 100644 --- a/mm/filemap.h +++ b/mm/filemap.h @@ -88,7 +88,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) const struct iovec *iov = *iovp; size_t base = *basep; - while (bytes) { + do { int copy = min(bytes, iov->iov_len - base); bytes -= copy; @@ -97,7 +97,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) iov++; base = 0; } - } + } while (bytes); *iovp = iov; *basep = base; } -- cgit v1.2.3-59-g8ed1b