[Samba] Weird behaviour opening pdf files (and maybe others)

[Jeremy Allison]

On Thu, Jul 14, 2016 at 11:39:37AM +0200, Alexandre wrote:
> Hi,
> 
> I had to review a samba setup recently where people experienced strange
> things.
> Basically they more from a solaris on phisical machines environment
> (locally hosted) running an old version of samba (2.x or even 1.x) to a Red
> Hat virtualized environement runing 3.6 (remotely hosted).
> The link between clients and server is really good (2x100Mb/s fiber) and
> browsing shares and opening office document is pretty good.
> However they are sharing some PDF files (half a MB each) and those are
> taking really long to open. When opened with Adobe reader from a windows
> machine, the PDF load by "slices". Some paragraph loads, and then another,
> and then another...
> Same behaviour can be seen with a linux client and xpdf (evince just takes
> ages to open the pdf).
> Raw transfers and copies (smbclient and windows drag and drop) works nicely.
> 
> The interesting bit:
> 
> The PDF files are actually stored on an NFS export on the EMC SAN storage.
> If I move the PDF files to another samba share with the same options but on
> a local filesystem, then the PDF loads nicely.
> 
> If I monitor the network traffic while opening a PDF file on the NFS
> export, I can see a lot of very short "smb read andX responses" (256 bytes
> long) and the total transfer size for a 500KB file is around 6MB.
> 
> If I monitor the network traffic while opening a PDF file on a local
> filesystem, I can see big "smb read andX responses" (65536 bytes as stated
> in smb.conf with "max xmit") and total transfer size is about equal to the
> file size.
> 
> the NFS export is mounted on the samba server using options:
> rw,noatime,nodiratime,bg,soft,rsize=65536,wsize=65536,nfsvers=3,proto=tcp,nocto,noacl,noac,int,nolock
> 
> 
> The cubersome bit:
> 
> At this point you can easily blame NFS (which i did) and claim sharing NFS
> exports via samba is just not a good idea (probably right anyway). BUT... a
> windows client that sits next to the samba server can open the problematic
> PDF files  without anyproblem, even if they are stored on the nfs exports!
> 
> I'd be interested to know if anybody already had the kind of problem and
> how they troubleshot/fixed it. Also if you have some idea where to look at
> just let me know.
> Finally, I have tried to find clear statement about sharing NFS exports via
> samba and wether or not it is suposed to work or what are the limitations.
> What's your opinion?

Sounds to me like no oplocks are being granted on the NFS share
export. That'd do it.