cvs commit: src/sys/nfsclient nfs_bio.c nfs_vfsops.c nfsargs.h nfsmount.h src/sys/sys buf.h bufobj.h src/sys/kern vfs_bio.c

[Brian Feldman]

green       2005-06-10 23:50:41 UTC

  FreeBSD src repository

  Modified files:
    sys/nfsclient        nfs_bio.c nfs_vfsops.c nfsargs.h 
                         nfsmount.h 
    sys/sys              buf.h bufobj.h 
    sys/kern             vfs_bio.c 
  Log:
  Fix a serious deadlock with the NFS client.  Given a large enough
  atomic write request, it can fill the buffer cache with the entirety
  of that write in order to handle retries.  However, it never drops
  the vnode lock, or else it wouldn't be atomic, so it ends up waiting
  indefinitely for more buf memory that cannot be gotten as it has it
  all, and it waits in an uncancellable state.
  
  To fix this, hibufspace is exported and scaled to a reasonable
  fraction.  This is used as the limit of how much of an atomic write
  request by the NFS client will be handled asynchronously.  If the
  request is larger than this, it will be turned into a synchronous
  request which won't deadlock the system.  It's possible this value is
  far off from what is required by some, so it shall be tunable as soon
  as mount_nfs(8) learns of the new field.
  
  The slowdown between an asynchronous and a synchronous write on NFS
  appears to be on the order of 2x-4x.
  
  General nod by: gad
  MFC after:      2 weeks
  More testing:   wes
  PR:             kern/79208
  
  Revision  Changes    Path
  1.489     +1 -1      src/sys/kern/vfs_bio.c
  1.151     +65 -0     src/sys/nfsclient/nfs_bio.c
  1.177     +9 -0      src/sys/nfsclient/nfs_vfsops.c
  1.68      +2 -2      src/sys/nfsclient/nfsargs.h
  1.30      +1 -0      src/sys/nfsclient/nfsmount.h
  1.186     +1 -0      src/sys/sys/buf.h
  1.15      +2 -2      src/sys/sys/bufobj.h