On Wed, 09 Apr 2008 17:57:56 +0200 Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > generic_file_splice_read() goes into an infinite loop if it races with > truncation. I've found this with fsx-linux on NFS over fuse. > > Perhaps the whole while() loop is bogus, but I can't tell from a > cursory glance at __generic_file_splice_read() if it will return zero > only on EOF, or it can do that for other reasons as well. In the > latter case the loop is obviously needed. > > This simplistic patch fixes the issue for me. > We found suspicious-looking code in generic_file_splice_read() back in February. See http://lkml.org/lkml/2008/2/29/443. I suspect that patch (if it works) will address the truncate lockup as well - it zaps the loop entirely. Unfortunately Allard never got back to us (probably because he's running 2.6.24 which has a quite different generic_file_splice_read()) and the patch didn't get anywhere. Here it is again. It needs a changelog. Nobody has tested this at all, to my knowledge. It's going to take some serious and sudden effort to get these bugs fixed for 2.6.25. fs/splice.c | 31 ++++++------------------------- 1 file changed, 6 insertions(+), 25 deletions(-) diff -puN fs/splice.c~generic_file_splice_read-fix-lockups fs/splice.c --- a/fs/splice.c~generic_file_splice_read-fix-lockups +++ a/fs/splice.c @@ -370,8 +370,10 @@ __generic_file_splice_read(struct file * * for an in-flight io page */ if (flags & SPLICE_F_NONBLOCK) { - if (TestSetPageLocked(page)) + if (TestSetPageLocked(page)) { + error = -EAGAIN; break; + } } else lock_page(page); @@ -479,9 +481,8 @@ ssize_t generic_file_splice_read(struct struct pipe_inode_info *pipe, size_t len, unsigned int flags) { - ssize_t spliced; - int ret; loff_t isize, left; + int ret; isize = i_size_read(in->f_mapping->host); if (unlikely(*ppos >= isize)) @@ -491,29 +492,9 @@ ssize_t generic_file_splice_read(struct if (unlikely(left < len)) len = left; - ret = 0; - spliced = 0; - while (len && !spliced) { - ret = __generic_file_splice_read(in, ppos, pipe, len, flags); - - if (ret < 0) - break; - else if (!ret) { - if (spliced) - break; - if (flags & SPLICE_F_NONBLOCK) { - ret = -EAGAIN; - break; - } - } - + ret = __generic_file_splice_read(in, ppos, pipe, len, flags); + if (ret > 0) *ppos += ret; - len -= ret; - spliced += ret; - } - - if (spliced) - return spliced; return ret; } _ -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
