| Message ID | 20180412150826.20988-32-mszeredi@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: > This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. > > No user of d_real_inode() remains, so it can be removed. > FYI, there is a new user in v4.17-rc1 added by commit f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs Seems like this patch got merged without any CC to overlayfs mailing list nor maintainer? Not sure yet if overlayfs-rorw patches would allow reverting this change. Thanks, Amir.
On Wed, Apr 18, 2018 at 10:19 AM, Amir Goldstein <amir73il@gmail.com> wrote: > On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: >> This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. >> >> No user of d_real_inode() remains, so it can be removed. >> > > FYI, there is a new user in v4.17-rc1 added by commit > f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs > > Seems like this patch got merged without any CC to overlayfs > mailing list nor maintainer? > > Not sure yet if overlayfs-rorw patches would allow reverting this > change. Not trivial, because uprobe is looking at i_mapping to get a list of current memory maps. We could set i_mapping at overlay inode initialization time, but we definitely can't *change* i_mapping at copy up. Which is bound to result in some weird inconsistencies. So likely we'll need to keep d_real_inode() for the time being. Thanks, Miklos
On Wed, 18 Apr 2018 13:42:03 +0200 Miklos Szeredi <miklos@szeredi.hu> wrote: > On Wed, Apr 18, 2018 at 10:19 AM, Amir Goldstein <amir73il@gmail.com> wrote: > > On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: > >> This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. > >> > >> No user of d_real_inode() remains, so it can be removed. > >> > > > > FYI, there is a new user in v4.17-rc1 added by commit > > f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs > > > > Seems like this patch got merged without any CC to overlayfs > > mailing list nor maintainer? It appeared to be a small change with lots of reviewers. I didn't think it was something to notify the overlayfs folks with. But perhaps I was wrong. > > > > Not sure yet if overlayfs-rorw patches would allow reverting this > > change. > > Not trivial, because uprobe is looking at i_mapping to get a list of > current memory maps. We could set i_mapping at overlay inode > initialization time, but we definitely can't *change* i_mapping at > copy up. Which is bound to result in some weird inconsistencies. So > likely we'll need to keep d_real_inode() for the time being. I just received this patch: http://lkml.kernel.org/r/20180418062907.3210386-1-songliubraving@fb.com Which removes this code. Can you review it and I'll take it. -- Steve
On Wed, Apr 18, 2018 at 3:38 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > On Wed, 18 Apr 2018 13:42:03 +0200 > Miklos Szeredi <miklos@szeredi.hu> wrote: > >> On Wed, Apr 18, 2018 at 10:19 AM, Amir Goldstein <amir73il@gmail.com> wrote: >> > On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: >> >> This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. >> >> >> >> No user of d_real_inode() remains, so it can be removed. >> >> >> > >> > FYI, there is a new user in v4.17-rc1 added by commit >> > f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs >> > >> > Seems like this patch got merged without any CC to overlayfs >> > mailing list nor maintainer? > > It appeared to be a small change with lots of reviewers. I didn't think > it was something to notify the overlayfs folks with. But perhaps I was > wrong. The patch is correct. The code surrounding it isn't, though. > >> > >> > Not sure yet if overlayfs-rorw patches would allow reverting this >> > change. >> >> Not trivial, because uprobe is looking at i_mapping to get a list of >> current memory maps. We could set i_mapping at overlay inode >> initialization time, but we definitely can't *change* i_mapping at >> copy up. Which is bound to result in some weird inconsistencies. So >> likely we'll need to keep d_real_inode() for the time being. > > I just received this patch: > > http://lkml.kernel.org/r/20180418062907.3210386-1-songliubraving@fb.com > > Which removes this code. Can you review it and I'll take it. It shouldn't remove d_real_inode(), because that part is correct and fixes a real bug in handling overlayfs files. I'll review, but apparently I wasn't CC-d on that patch. Weird. Thanks, Miklos
On Wed, 18 Apr 2018 15:49:02 +0200 Miklos Szeredi <miklos@szeredi.hu> wrote: > > I just received this patch: > > > > http://lkml.kernel.org/r/20180418062907.3210386-1-songliubraving@fb.com > > > > Which removes this code. Can you review it and I'll take it. > > It shouldn't remove d_real_inode(), because that part is correct and > fixes a real bug in handling overlayfs files. > > I'll review, but apparently I wasn't CC-d on that patch. Weird. Especially since you are on the "Reported-by". My scripts know to add to the Cc "Reported-by" tags. Not all scripts do though :-/ -- Steve
On Wed, Apr 18, 2018 at 03:49:02PM +0200, Miklos Szeredi wrote: > On Wed, Apr 18, 2018 at 3:38 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 18 Apr 2018 13:42:03 +0200 > > Miklos Szeredi <miklos@szeredi.hu> wrote: > > > >> On Wed, Apr 18, 2018 at 10:19 AM, Amir Goldstein <amir73il@gmail.com> wrote: > >> > On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: > >> >> This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. > >> >> > >> >> No user of d_real_inode() remains, so it can be removed. > >> >> > >> > > >> > FYI, there is a new user in v4.17-rc1 added by commit > >> > f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs > >> > > >> > Seems like this patch got merged without any CC to overlayfs > >> > mailing list nor maintainer? > > > > It appeared to be a small change with lots of reviewers. I didn't think > > it was something to notify the overlayfs folks with. But perhaps I was > > wrong. > > The patch is correct. The code surrounding it isn't, though. > > > > >> > > >> > Not sure yet if overlayfs-rorw patches would allow reverting this > >> > change. > >> > >> Not trivial, because uprobe is looking at i_mapping to get a list of > >> current memory maps. We could set i_mapping at overlay inode > >> initialization time, but we definitely can't *change* i_mapping at > >> copy up. Which is bound to result in some weird inconsistencies. So > >> likely we'll need to keep d_real_inode() for the time being. > > > > I just received this patch: > > > > http://lkml.kernel.org/r/20180418062907.3210386-1-songliubraving@fb.com > > > > Which removes this code. Can you review it and I'll take it. > > It shouldn't remove d_real_inode(), because that part is correct and > fixes a real bug in handling overlayfs files. I am wondering what does it practically mean for metdata only copy up patches. Given this is uprobe code, I am assuming its modifying some executable code dynamically. And for the the case of metadata only copy up, it will return inode of lower. That probably means, as long as all running instances of that exeutable are using that inode, things will work fine. But if for some reason somebody opens that file for WRITE and triggers copy up and new instances of same binary will not see the probe taking affect? Which is probably very similar to what will happen if a lower executable is copied up. Having said that, in normal cases there should not be a need to copy up a binary in normal circumstances. Am I missing the point completely. Thanks Vivek
On Thu, Apr 19, 2018 at 9:54 PM, Vivek Goyal <vgoyal@redhat.com> wrote: > On Wed, Apr 18, 2018 at 03:49:02PM +0200, Miklos Szeredi wrote: >> On Wed, Apr 18, 2018 at 3:38 PM, Steven Rostedt <rostedt@goodmis.org> wrote: >> > On Wed, 18 Apr 2018 13:42:03 +0200 >> > Miklos Szeredi <miklos@szeredi.hu> wrote: >> > >> >> On Wed, Apr 18, 2018 at 10:19 AM, Amir Goldstein <amir73il@gmail.com> wrote: >> >> > On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote: >> >> >> This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. >> >> >> >> >> >> No user of d_real_inode() remains, so it can be removed. >> >> >> >> >> > >> >> > FYI, there is a new user in v4.17-rc1 added by commit >> >> > f0a2aa5a2a40 tracing/uprobe: Add support for overlayfs >> >> > >> >> > Seems like this patch got merged without any CC to overlayfs >> >> > mailing list nor maintainer? >> > >> > It appeared to be a small change with lots of reviewers. I didn't think >> > it was something to notify the overlayfs folks with. But perhaps I was >> > wrong. >> >> The patch is correct. The code surrounding it isn't, though. >> >> > >> >> > >> >> > Not sure yet if overlayfs-rorw patches would allow reverting this >> >> > change. >> >> >> >> Not trivial, because uprobe is looking at i_mapping to get a list of >> >> current memory maps. We could set i_mapping at overlay inode >> >> initialization time, but we definitely can't *change* i_mapping at >> >> copy up. Which is bound to result in some weird inconsistencies. So >> >> likely we'll need to keep d_real_inode() for the time being. >> > >> > I just received this patch: >> > >> > http://lkml.kernel.org/r/20180418062907.3210386-1-songliubraving@fb.com >> > >> > Which removes this code. Can you review it and I'll take it. >> >> It shouldn't remove d_real_inode(), because that part is correct and >> fixes a real bug in handling overlayfs files. > > I am wondering what does it practically mean for metdata only copy up > patches. Given this is uprobe code, I am assuming its modifying some > executable code dynamically. And for the the case of metadata only > copy up, it will return inode of lower. That probably means, as long > as all running instances of that exeutable are using that inode, things > will work fine. > > But if for some reason somebody opens that file for WRITE and triggers > copy up and new instances of same binary will not see the probe taking > affect? > > Which is probably very similar to what will happen if a lower executable > is copied up. Having said that, in normal cases there should not be a > need to copy up a binary in normal circumstances. The only thing we need to ensure when uprobes interact with copy-ups is that the kernel doesn't crash and doesn't leak memory. Other than that, it's a totally uninteresting corner case and we don't need to worry about its behavior. Thanks, Miklos
diff --git a/include/linux/dcache.h b/include/linux/dcache.h index c2dea5e78f54..129ef05759a9 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -586,18 +586,6 @@ static inline struct dentry *d_real(struct dentry *dentry, return dentry; } -/** - * d_real_inode - Return the real inode - * @dentry: The dentry to query - * - * If dentry is on a union/overlay, then return the underlying, real inode. - * Otherwise return d_inode(). - */ -static inline struct inode *d_real_inode(struct dentry *dentry) -{ - return d_backing_inode(d_real(dentry, NULL, 0)); -} - struct name_snapshot { const unsigned char *name; unsigned char inline_name[DNAME_INLINE_LEN];
This reverts commit a118084432d642eeccb961c7c8cc61525a941fcb. No user of d_real_inode() remains, so it can be removed. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- include/linux/dcache.h | 12 ------------ 1 file changed, 12 deletions(-)