Messages in this thread | | | Date | Fri, 14 Jan 2011 17:44:42 +0800 | From | Américo Wang <> | Subject | Re: [PATCH] /proc/kcore: fix seeking |
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On Tue, Jan 11, 2011 at 05:23:23PM +0100, Frederic Weisbecker wrote: >On Wed, Jan 12, 2011 at 12:04:37AM +0800, Américo Wang wrote: >> On Mon, Jan 10, 2011 at 09:42:29AM -0500, Dave Anderson wrote: >> >From: Dave Anderson <anderson@redhat.com> >> > >> >Commit 34aacb2920667d405a8df15968b7f71ba46c8f18 >> >("procfs: Use generic_file_llseek in /proc/kcore") >> >broke seeking on /proc/kcore. This changes it back >> >to use default_llseek in order to restore the original >> >behavior. >> > >> >The problem with generic_file_llseek is that it only >> >allows seeks up to inode->i_sb->s_maxbytes, which is >> >2GB-1 on procfs, where the memory file offset values in >> >the /proc/kcore PT_LOAD segments may exceed or start >> >beyond that offset value. >> > >> >> Is the race solved? Using default_llseek() still races >> with read_kcore() on fpos, AFAIK. > >Hmm, how does it race there? > >read_kcore() manipulates fpos, which can't be changed behind >us inside the read callback as it's a snapshot. Also read_kcore() >can change the value of fpos, which is writed back to file->fpos >from sys_read(). > >So the last resulting race here the natural one between >seeking and reading, which is up to the user to take care >of.
Hmm, I just read the changelog of commit 34aacb2920667d405a8df15968b7f71ba46c8f18, which claims to fix the race. So anything changed in vfs layer after that?
Thanks.
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