/share/man/man9/vrele.9

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  1. .\" -*- nroff -*-
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  2. .\"
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  3. .\" Copyright (c) 1996 Doug Rabson
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  4. .\" Copyright (c) 2010 Konstantin Belousov <kib@FreeBSD.org>
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  6. .\" All rights reserved.
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  32. .Dd November 20, 2010
    33. 

  33. .Dt VRELE 9
    34. 

  34. .Os
    35. 

  35. .Sh NAME
    36. 

  36. .Nm vput ,
    37. 

  37. .Nm vrele ,
    38. 

  38. .Nm vunref
    39. 

  39. .Nd decrement the use count for a vnode
    40. 

  40. .Sh SYNOPSIS
    41. 

  41. .In sys/param.h
    42. 

  42. .In sys/vnode.h
    43. 

  43. .Ft void
    44. 

  44. .Fn vput "struct vnode *vp"
    45. 

  45. .Ft void
    46. 

  46. .Fn vrele "struct vnode *vp"
    47. 

  47. .Ft void
    48. 

  48. .Fn vunref "struct vnode *vp"
    49. 

  49. .Sh DESCRIPTION
    50. 

  50. Decrement the
    51. 

  51. .Va v_usecount
    52. 

  52. field of a vnode.
    53. 

  53. .Bl -tag -width 2n
    54. 

  54. .It Fa vp
    55. 

  55. the vnode to decrement
    56. 

  56. .El
    57. 

  57. .Pp
    58. 

  58. The
    59. 

  59. .Fn vrele
    60. 

  60. function takes an unlocked vnode and returns with the vnode unlocked.
    61. 

  61. .Pp
    62. 

  62. The
    63. 

  63. .Fn vput
    64. 

  64. function should be given a locked vnode as argument, the vnode is unlocked
    65. 

  65. after the function returned.
    66. 

  66. The
    67. 

  67. .Fn vput
    68. 

  68. is operationally equivalent to calling
    69. 

  69. .Xr VOP_UNLOCK 9
    70. 

  70. followed by
    71. 

  71. .Xr vrele 9 ,
    72. 

  72. with less overhead.
    73. 

  73. .Pp
    74. 

  74. The
    75. 

  75. .Fn vunref
    76. 

  76. function takes a locked vnode as argument, and returns with the vnode locked.
    77. 

  77. .Pp
    78. 

  78. Any code in the system which signified its use of a vnode by usecount
    79. 

  79. should call one of the listed function to decrement use counter.
    80. 

  80. If the
    81. 

  81. .Va v_usecount
    82. 

  82. field of the non-doomed vnode reaches zero, then it will be inactivated
    83. 

  83. and placed on the free list.
    84. 

  84. Since the functions might need to call VOPs for the vnode, the
    85. 

  85. .Va Giant
    86. 

  86. mutex should be conditionally locked around the call.
    87. 

  87. .Pp
    88. 

  88. The hold count for the vnode is always greater or equal to the usecount.
    89. 

  89. Non-forced unmount fails when mount point owns a vnode that has non-zero
    90. 

  90. usecount, see
    91. 

  91. .Xr vflush 9 .
    92. 

  92. .Sh SEE ALSO
    93. 

  93. .Xr vget 9 ,
    94. 

  94. .Xr vnode 9 ,
    95. 

  95. .Xr vref 9 ,
    96. 

  96. .Xr vrefcnt 9
    97. 

  97. .Sh AUTHORS
    98. 

  98. This manual page was written by
    99. 

  99. .An Doug Rabson
    100. 

  100. and
    101. 

  101. .An Konstantin Belousov .
    102.