Linux: will file reads from CIFS be cached in memory?

Question

I am writing a streaming server for linux that reads files from CIFS mounts and sends them over a socket. Ideally, linux will cache the file in memory so that subsequent reads will be faster. Is this the case? Can I tell the kernel to cache network reads ?

Edit: there will be multiple reads, but no writes, on these files.

Thanks!

Update: I've tested this on a CIFS volume, using fadvise POSIX_FADV_WILLNEED to cache the file locally (using linux-ftools on command line). Turns out that the volume needs to be mounted in read-write mode for this to work. In read only mode, the fadvise seems to be ignored. This must have something to do with the samba oplock mechanism.

Answer 1

Subject to the usual cache coherency rules [1] in CIFS, yes, the kernel CIFS client will cache file data.

[1] Roughly, CIFS is uncached in principle, but by taking oplocks the client can cache data more aggressively. For an explanation of CIFS locking, see e.g. the Samba manual at http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/locking.html . If the client(s) open the files in read only mode, then I suspect the client will use level 2 oplocks, and as there's no conflicting access takes place, multiple clients should be able to have level 2 oplocks for the same files. Only when some client requests write access to the files, will the oplocks be broken.