Messages in this thread Patch in this message |  | | | Date | Wed, 28 Jun 2006 22:20:36 -0700 | | From | Andrew Morton <> | | Subject | Re: Unkillable process in last git -- Bisected |
| |
On Wed, 28 Jun 2006 20:38:25 +0200 Paolo Ornati <ornati@fastwebnet.it> wrote:
> After a git-bisect session I've found that reverting the following > commit fixes the problem. > > Any idea? > > > commit 6527c2bdf1f833cc18e8f42bd97973d583e4aa83 > Author: Vladimir V. Saveliev <vs@namesys.com> > Date: Tue Jun 27 02:53:57 2006 -0700 > > [PATCH] generic_file_buffered_write(): deadlock on vectored write
From: Andrew Morton <akpm@osdl.org>
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> --- mm/filemap.c | 9 ++++++++- mm/filemap.h | 4 ++-- 2 files changed, 10 insertions(+), 3 deletions(-) diff -puN mm/filemap.c~generic_file_buffered_write-handle-zero-length-iovec-segments-stable mm/filemap.c --- a/mm/filemap.c~generic_file_buffered_write-handle-zero-length-iovec-segments-stable +++ a/mm/filemap.c @@ -2125,6 +2125,12 @@ generic_file_buffered_write(struct kiocb break; } + if (unlikely(bytes == 0)) { + status = 0; + copied = 0; + goto zero_length_segment; + } + status = a_ops->prepare_write(file, page, offset, offset+bytes); if (unlikely(status)) { loff_t isize = i_size_read(inode); @@ -2154,7 +2160,8 @@ generic_file_buffered_write(struct kiocb page_cache_release(page); continue; } - if (likely(copied > 0)) { +zero_length_segment: + if (likely(copied >= 0)) { if (!status) status = copied; diff -puN mm/filemap.h~generic_file_buffered_write-handle-zero-length-iovec-segments-stable mm/filemap.h --- a/mm/filemap.h~generic_file_buffered_write-handle-zero-length-iovec-segments-stable +++ a/mm/filemap.h @@ -88,7 +88,7 @@ filemap_set_next_iovec(const struct iove 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 iove iov++; base = 0; } - } + } while (bytes); *iovp = iov; *basep = base; } _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |