Messages in this thread | | | Date | Thu, 21 Mar 2013 12:48:36 +0800 | Subject | Re: [PATCH 1/2] sysfs: fix race between readdir and lseek | From | Ming Lei <> |
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On Thu, Mar 21, 2013 at 11:28 AM, Li Zefan <lizefan@huawei.com> wrote: > On 2013/3/21 11:17, Ming Lei wrote: >> On Thu, Mar 21, 2013 at 10:41 AM, Li Zefan <lizefan@huawei.com> wrote: >>> >>> In fact the same race exists between readdir() and read()/write()... >> >> Fortunately, no read()/write() are implemented on sysfs directory, :-) >> > > That's irrelevant...
As far as sysfs is concerned, the filp->f_ops can't be changed in read/write path.
> > See my report: > > https://patchwork.kernel.org/patch/2160771/
Yes, I know there might be some mess after the commit ef3d0fd2 (vfs: do (nearly) lockless generic_file_llseek).
Also looks it has been stated in Documentation/filesystems/Locking:
->llseek() locking has moved from llseek to the individual llseek implementations. If your fs is not using generic_file_llseek, you need to acquire and release the appropriate locks in your ->llseek(). For many filesystems, it is probably safe to acquire the inode mutex or just to use i_size_read() instead. Note: this does not protect the file->f_pos against concurrent modifications since this is something the userspace has to take care about.
Thanks, -- Ming Lei
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