| Message ID | 4E5BA855.2030109@netapp.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Aug 29, 2011, at 10:55 AM, Bryan Schumaker wrote: > On 08/29/2011 10:43 AM, Chuck Lever wrote: >> >> On Aug 29, 2011, at 9:46 AM, Bryan Schumaker wrote: >> >>> On 08/27/2011 07:52 PM, Chuck Lever wrote: >>>> >>>> On Aug 26, 2011, at 4:52 PM, Bryan Schumaker wrote: >>>> >>>>> nfsiostat was failing to find mounted filesystems on recent kernels due >>>>> to changes in the VFS that resulted in a missing "device" tag in the >>>>> /proc/self/mountstats file. >>>> >>>> What was the commit ID that changed this formal kernel API? I'd like to see the justification. >>> >>> It was changed by this commit: >>> >>> commit c7f404b40a3665d9f4e9a927cc5c1ee0479ed8f9 >>> Author: Al Viro <viro@zeniv.linux.org.uk> >>> Date: Wed Mar 16 06:59:40 2011 -0400 >>> >>> vfs: new superblock methods to override /proc/*/mount{s,info} >>> >>> a) ->show_devname(m, mnt) - what to put into devname columns in mounts, >>> mountinfo and mountstats >>> b) ->show_path(m, mnt) - what to put into relative path column in mountinfo >>> >>> Leaving those NULL gives old behaviour. NFS switched to using those. >>> >>> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> >> >> It looks like dropping the "device" tag from /proc/self/mountstats was not intentional, so this is a kernel API regression. At a guess, 2.6.39 probably works right, but 3.0 is broken. Whatever solution we come up with might need to be cc:d to stable@kernel.org. Be sure to verify which released kernels are broken. > > I'll double check that 39 works. >> >> Does changing nfs_show_devname() to add a "device" tag have any effect on the other two /proc files (mounts and mountinfo)? I suspect you do want to fix show_vfsstat() instead of nfs_show_devname(). This should add "device" only where it is needed, and would work for all file systems. > > Yeah, looks like it changes both. I'm looking at show_vfsstat() now, but nfs_show_devname() will return an error if a call to nfs_path() fails. This would probably result in an empty "device " line printed to /proc/self/mountstats. Do you know if that would be a problem for anything? The only error return from nfs_path() is if the name is too long. You could change nfs_show_devname() to output a fixed error string in that case (like "path too long"), or something even more generic. > I'm thinking about doing something like this: > > diff --git a/fs/namespace.c b/fs/namespace.c > index 22bfe82..1429114 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -1109,6 +1109,7 @@ static int show_vfsstat(struct seq_file *m, void *v) > > /* device */ > if (mnt->mnt_sb->s_op->show_devname) { > + seq_puts(m, "device "); > err = mnt->mnt_sb->s_op->show_devname(m, mnt); > } else { > if (mnt->mnt_devname) { There probably isn't a clean way to have just one seq_puts(m, "device "); invocation in this function. > > >> >>> >>> >>>> >>>>> This patch re-adds the "device" tag for NFS >>>>> mount data in /proc/self/mountstats. >>>> >>>> The purpose of mountstats is to be an interface that all file systems can use. If we can't add "device" back to all mounts listed in /proc/self/mountstats, it might be better to adjust nfsiostats to cope. >>>> >>>>> Signed-off-by: Bryan Schumaker <bjschuma@netapp.com> >>>>> --- >>>>> fs/nfs/super.c | 4 +++- >>>>> 1 files changed, 3 insertions(+), 1 deletions(-) >>>>> >>>>> diff --git a/fs/nfs/super.c b/fs/nfs/super.c >>>>> index b961cea..e6a0317 100644 >>>>> --- a/fs/nfs/super.c >>>>> +++ b/fs/nfs/super.c >>>>> @@ -766,8 +766,10 @@ static int nfs_show_devname(struct seq_file *m, struct vfsmount *mnt) >>>>> devname = nfs_path(&dummy, mnt->mnt_root, page, PAGE_SIZE); >>>>> if (IS_ERR(devname)) >>>>> err = PTR_ERR(devname); >>>>> - else >>>>> + else { >>>>> + seq_puts(m, "device "); >>>>> seq_escape(m, devname, " \t\n\\"); >>>>> + } >>>>> free_page((unsigned long)page); >>>>> return err; >>>>> } >>>>> -- >>>>> 1.7.6 >>>> >>> >> >
diff --git a/fs/namespace.c b/fs/namespace.c index 22bfe82..1429114 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1109,6 +1109,7 @@ static int show_vfsstat(struct seq_file *m, void *v) /* device */ if (mnt->mnt_sb->s_op->show_devname) { + seq_puts(m, "device "); err = mnt->mnt_sb->s_op->show_devname(m, mnt); } else { if (mnt->mnt_devname) {