Skip to content

K
Kernel

openeuler / Kernel
接近 2 年 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 03 11月, 2011 4 次提交
  3. 28 10月, 2011 2 次提交
    • A
      nfs: drop unnecessary locking in llseek · 79835a71
      由 Andi Kleen 提交于 
      This makes NFS follow the standard generic_file_llseek locking scheme.

Cc: Trond.Myklebust@netapp.com
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
      79835a71
    • A
      vfs: do (nearly) lockless generic_file_llseek · ef3d0fd2
      由 Andi Kleen 提交于 
      The i_mutex lock use of generic _file_llseek hurts.  Independent processes
accessing the same file synchronize over a single lock, even though
they have no need for synchronization at all.

Under high utilization this can cause llseek to scale very poorly on larger
systems.

This patch does some rethinking of the llseek locking model:

First the 64bit f_pos is not necessarily atomic without locks
on 32bit systems. This can already cause races with read() today.
This was discussed on linux-kernel in the past and deemed acceptable.
The patch does not change that.

Let's look at the different seek variants:

SEEK_SET: Doesn't really need any locking.
If there's a race one writer wins, the other loses.

For 32bit the non atomic update races against read()
stay the same. Without a lock they can also happen
against write() now.  The read() race was deemed
acceptable in past discussions, and I think if it's
ok for read it's ok for write too.

=> Don't need a lock.

SEEK_END: This behaves like SEEK_SET plus it reads
the maximum size too. Reading the maximum size would have the
32bit atomic problem. But luckily we already have a way to read
the maximum size without locking (i_size_read), so we
can just use that instead.

Without i_mutex there is no synchronization with write() anymore,
however since the write() update is atomic on 64bit it just behaves
like another racy SEEK_SET.  On non atomic 32bit it's the same
as SEEK_SET.

=> Don't need a lock, but need to use i_size_read()

SEEK_CUR: This has a read-modify-write race window
on the same file. One could argue that any application
doing unsynchronized seeks on the same file is already broken.
But for the sake of not adding a regression here I'm
using the file->f_lock to synchronize this. Using this
lock is much better than the inode mutex because it doesn't
synchronize between processes.

=> So still need a lock, but can use a f_lock.

This patch implements this new scheme in generic_file_llseek.
I dropped generic_file_llseek_unlocked and changed all callers.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
      ef3d0fd2
  5. 21 10月, 2011 1 次提交
  7. 20 10月, 2011 4 次提交
  9. 19 10月, 2011 17 次提交
  11. 12 10月, 2011 1 次提交
  13. 27 9月, 2011 1 次提交
  15. 14 9月, 2011 2 次提交
    • S
      nfs: Do not allow multiple mounts on same mountpoint when using -o noac · fb2088cc
      由 Sachin Prabhu 提交于 
      Do not allow multiple mounts on same mountpoint when using -o noac

When you normally attempt to mount a share twice on the same mountpoint,
a check in do_add_mount causes it to return an error

# mount localhost:/nfsv3 /mnt
# mount localhost:/nfsv3 /mnt
mount.nfs: /mnt is already mounted or busy

However when using the option 'noac', the user is able to mount the same
share on the same mountpoint multiple times. This happens because a
share mounted with the noac option is automatically assigned the 'sync'
flag MS_SYNCHRONOUS in nfs_initialise_sb(). This flag is set after the
check for already existing superblocks is done in sget(). The check for
the mount flags in nfs_compare_mount_options() does not take into
account the 'sync' flag applied later on in the code path. This means
that when using 'noac', a new superblock structure is assigned for every
new mount of the same share and multiple shares on the same mountpoint
are allowed.

ie.
# mount -onoac localhost:/nfsv3 /mnt
can be run multiple times.

The patch checks for noac and assigns the sync flag before sget() is
called to obtain an already existing superblock structure.
Signed-off-by: NSachin Prabhu <sprabhu@redhat.com>
Reviewed-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
      fb2088cc
    • T
      NFS: Fix a typo in nfs_flush_multi · f13c3620
      由 Trond Myklebust 提交于 
      Fix a typo which causes an Oops in the RPC layer, when using wsize < 4k.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: NSricharan R <r.sricharan@ti.com>
      f13c3620
  17. 28 8月, 2011 1 次提交
  19. 25 8月, 2011 4 次提交
  21. 20 8月, 2011 1 次提交
  23. 12 8月, 2011 1 次提交
  25. 11 8月, 2011 1 次提交