fs/xfs/xfs_filestream.h

   1 /*
   2  * Copyright (c) 2006-2007 Silicon Graphics, Inc.
   3  * All Rights Reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it would be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write the Free Software Foundation,
  16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18 #ifndef __XFS_FILESTREAM_H__
  19 #define __XFS_FILESTREAM_H__
  20
  21 #ifdef __KERNEL__
  22
  23 struct xfs_mount;
  24 struct xfs_inode;
  25 struct xfs_perag;
  26 struct xfs_bmalloca;
  27
  28 #ifdef XFS_FILESTREAMS_TRACE
  29 #define XFS_FSTRM_KTRACE_INFO           1
  30 #define XFS_FSTRM_KTRACE_AGSCAN         2
  31 #define XFS_FSTRM_KTRACE_AGPICK1        3
  32 #define XFS_FSTRM_KTRACE_AGPICK2        4
  33 #define XFS_FSTRM_KTRACE_UPDATE         5
  34 #define XFS_FSTRM_KTRACE_FREE           6
  35 #define XFS_FSTRM_KTRACE_ITEM_LOOKUP    7
  36 #define XFS_FSTRM_KTRACE_ASSOCIATE      8
  37 #define XFS_FSTRM_KTRACE_MOVEAG         9
  38 #define XFS_FSTRM_KTRACE_ORPHAN         10
  39
  40 #define XFS_FSTRM_KTRACE_SIZE   16384
  41 extern ktrace_t *xfs_filestreams_trace_buf;
  42
  43 #endif
  44
  45 /*
  46  * Allocation group filestream associations are tracked with per-ag atomic
  47  * counters.  These counters allow _xfs_filestream_pick_ag() to tell whether a
  48  * particular AG already has active filestreams associated with it. The mount
  49  * point's m_peraglock is used to protect these counters from per-ag array
  50  * re-allocation during a growfs operation.  When xfs_growfs_data_private() is
  51  * about to reallocate the array, it calls xfs_filestream_flush() with the
  52  * m_peraglock held in write mode.
  53  *
  54  * Since xfs_mru_cache_flush() guarantees that all the free functions for all
  55  * the cache elements have finished executing before it returns, it's safe for
  56  * the free functions to use the atomic counters without m_peraglock protection.
  57  * This allows the implementation of xfs_fstrm_free_func() to be agnostic about
  58  * whether it was called with the m_peraglock held in read mode, write mode or
  59  * not held at all.  The race condition this addresses is the following:
  60  *
  61  *  - The work queue scheduler fires and pulls a filestream directory cache
  62  *    element off the LRU end of the cache for deletion, then gets pre-empted.
  63  *  - A growfs operation grabs the m_peraglock in write mode, flushes all the
  64  *    remaining items from the cache and reallocates the mount point's per-ag
  65  *    array, resetting all the counters to zero.
  66  *  - The work queue thread resumes and calls the free function for the element
  67  *    it started cleaning up earlier.  In the process it decrements the
  68  *    filestreams counter for an AG that now has no references.
  69  *
  70  * With a shrinkfs feature, the above scenario could panic the system.
  71  *
  72  * All other uses of the following macros should be protected by either the
  73  * m_peraglock held in read mode, or the cache's internal locking exposed by the
  74  * interval between a call to xfs_mru_cache_lookup() and a call to
  75  * xfs_mru_cache_done().  In addition, the m_peraglock must be held in read mode
  76  * when new elements are added to the cache.
  77  *
  78  * Combined, these locking rules ensure that no associations will ever exist in
  79  * the cache that reference per-ag array elements that have since been
  80  * reallocated.
  81  */
  82 static inline int
  83 xfs_filestream_peek_ag(
  84         xfs_mount_t     *mp,
  85         xfs_agnumber_t  agno)
  86 {
  87         return atomic_read(&mp->m_perag[agno].pagf_fstrms);
  88 }
  89
  90 static inline int
  91 xfs_filestream_get_ag(
  92         xfs_mount_t     *mp,
  93         xfs_agnumber_t  agno)
  94 {
  95         return atomic_inc_return(&mp->m_perag[agno].pagf_fstrms);
  96 }
  97
  98 static inline int
  99 xfs_filestream_put_ag(
 100         xfs_mount_t     *mp,
 101         xfs_agnumber_t  agno)
 102 {
 103         return atomic_dec_return(&mp->m_perag[agno].pagf_fstrms);
 104 }
 105
 106 /* allocation selection flags */
 107 typedef enum xfs_fstrm_alloc {
 108         XFS_PICK_USERDATA = 1,
 109         XFS_PICK_LOWSPACE = 2,
 110 } xfs_fstrm_alloc_t;
 111
 112 /* prototypes for filestream.c */
 113 int xfs_filestream_init(void);
 114 void xfs_filestream_uninit(void);
 115 int xfs_filestream_mount(struct xfs_mount *mp);
 116 void xfs_filestream_unmount(struct xfs_mount *mp);
 117 void xfs_filestream_flush(struct xfs_mount *mp);
 118 xfs_agnumber_t xfs_filestream_lookup_ag(struct xfs_inode *ip);
 119 int xfs_filestream_associate(struct xfs_inode *dip, struct xfs_inode *ip);
 120 void xfs_filestream_deassociate(struct xfs_inode *ip);
 121 int xfs_filestream_new_ag(struct xfs_bmalloca *ap, xfs_agnumber_t *agp);
 122
 123
 124 /* filestreams for the inode? */
 125 static inline int
 126 xfs_inode_is_filestream(
 127         struct xfs_inode        *ip)
 128 {
 129         return (ip->i_mount->m_flags & XFS_MOUNT_FILESTREAMS) ||
 130                 xfs_iflags_test(ip, XFS_IFILESTREAM) ||
 131                 (ip->i_d.di_flags & XFS_DIFLAG_FILESTREAM);
 132 }
 133
 134 #endif /* __KERNEL__ */
 135
 136 #endif /* __XFS_FILESTREAM_H__ */