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  1. 02 Aug, 2017 1 commit
  3. 01 Aug, 2017 1 commit
  5. 28 Jul, 2017 1 commit
    • Benjamin Coddington's avatar
      NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter · b7dbcc0e
      Benjamin Coddington authored 
      nfs4_retry_setlk() sets the task's state to TASK_INTERRUPTIBLE within the
same region protected by the wait_queue's lock after checking for a
notification from CB_NOTIFY_LOCK callback.  However, after releasing that
lock, a wakeup for that task may race in before the call to
freezable_schedule_timeout_interruptible() and set TASK_WAKING, then
freezable_schedule_timeout_interruptible() will set the state back to
TASK_INTERRUPTIBLE before the task will sleep.  The result is that the task
will sleep for the entire duration of the timeout.

Since we've already set TASK_INTERRUPTIBLE in the locked section, just use
freezable_schedule_timout() instead.

Fixes: a1d617d8 ("nfs: allow blocking locks to be awoken by lock callbacks")
Signed-off-by: default avatarBenjamin Coddington <bcodding@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
      b7dbcc0e
  7. 27 Jul, 2017 2 commits
    • NeilBrown's avatar
      NFS: Optimize fallocate by refreshing mapping when needed. · 6ba80d43
      NeilBrown authored 
      posix_fallocate() will allocate space in an NFS file by considering
the last byte of every 4K block.  If it is before EOF, it will read
the byte and if it is zero, a zero is written out.  If it is after EOF,
the zero is unconditionally written.

For the blocks beyond EOF, if NFS believes its cache is valid, it will
expand these writes to write full pages, and then will merge the pages.
This results if (typically) 1MB writes.  If NFS believes its cache is
not valid (particularly if NFS_INO_INVALID_DATA or
NFS_INO_REVAL_PAGECACHE are set - see nfs_write_pageuptodate()), it will
send the individual 1-byte writes. This results in (typically) 256 times
as many RPC requests, and can be substantially slower.

Currently nfs_revalidate_mapping() is only used when reading a file or
mmapping a file, as these are times when the content needs to be
up-to-date.  Writes don't generally need the cache to be up-to-date, but
writes beyond EOF can benefit, particularly in the posix_fallocate()
case.

So this patch calls nfs_revalidate_mapping() when writing beyond EOF -
i.e. when there is a gap between the end of the file and the start of
the write.  If the cache is thought to be out of date (as happens after
taking a file lock), this will cause a GETATTR, and the two flags
mentioned above will be cleared.  With this, posix_fallocate() on a
newly locked file does not generate excessive tiny writes.
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
      6ba80d43
    • NeilBrown's avatar
      NFS: invalidate file size when taking a lock. · 442ce049
      NeilBrown authored 
      Prior to commit ca0daa27 ("NFS: Cache aggressively when file is open
for writing"), NFS would revalidate, or invalidate, the file size when
taking a lock.  Since that commit it only invalidates the file content.

If the file size is changed on the server while wait for the lock, the
client will have an incorrect understanding of the file size and could
corrupt data.  This particularly happens when writing beyond the
(supposed) end of file and can be easily be demonstrated with
posix_fallocate().

If an application opens an empty file, waits for a write lock, and then
calls posix_fallocate(), glibc will determine that the underlying
filesystem doesn't support fallocate (assuming version 4.1 or earlier)
and will write out a '0' byte at the end of each 4K page in the region
being fallocated that is after the end of the file.
NFS will (usually) detect that these writes are beyond EOF and will
expand them to cover the whole page, and then will merge the pages.
Consequently, NFS will write out large blocks of zeroes beyond where it
thought EOF was.  If EOF had moved, the pre-existing part of the file
will be over-written.  Locking should have protected against this,
but it doesn't.

This patch restores the use of nfs_zap_caches() which invalidated the
cached attributes.  When posix_fallocate() asks for the file size, the
request will go to the server and get a correct answer.

cc: stable@vger.kernel.org (v4.8+)
Fixes: ca0daa27 ("NFS: Cache aggressively when file is open for writing")
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
      442ce049
  9. 26 Jul, 2017 1 commit
  11. 21 Jul, 2017 7 commits
  13. 19 Jul, 2017 5 commits
  15. 13 Jul, 2017 22 commits
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