diff options
Diffstat (limited to 'fs/xfs/xfs_filestream.h')
| -rw-r--r-- | fs/xfs/xfs_filestream.h | 82 |
1 files changed, 0 insertions, 82 deletions
diff --git a/fs/xfs/xfs_filestream.h b/fs/xfs/xfs_filestream.h index 260f757bbc5d..09dd9af45434 100644 --- a/fs/xfs/xfs_filestream.h +++ b/fs/xfs/xfs_filestream.h | |||
| @@ -42,88 +42,6 @@ extern ktrace_t *xfs_filestreams_trace_buf; | |||
| 42 | 42 | ||
| 43 | #endif | 43 | #endif |
| 44 | 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 | /* | ||
| 83 | * xfs_filestream_peek_ag is only used in tracing code | ||
| 84 | */ | ||
| 85 | static inline int | ||
| 86 | xfs_filestream_peek_ag( | ||
| 87 | xfs_mount_t *mp, | ||
| 88 | xfs_agnumber_t agno) | ||
| 89 | { | ||
| 90 | struct xfs_perag *pag; | ||
| 91 | int ret; | ||
| 92 | |||
| 93 | pag = xfs_perag_get(mp, agno); | ||
| 94 | ret = atomic_read(&pag->pagf_fstrms); | ||
| 95 | xfs_perag_put(pag); | ||
| 96 | return ret; | ||
| 97 | } | ||
| 98 | |||
| 99 | static inline int | ||
| 100 | xfs_filestream_get_ag( | ||
| 101 | xfs_mount_t *mp, | ||
| 102 | xfs_agnumber_t agno) | ||
| 103 | { | ||
| 104 | struct xfs_perag *pag; | ||
| 105 | int ret; | ||
| 106 | |||
| 107 | pag = xfs_perag_get(mp, agno); | ||
| 108 | ret = atomic_inc_return(&pag->pagf_fstrms); | ||
| 109 | xfs_perag_put(pag); | ||
| 110 | return ret; | ||
| 111 | } | ||
| 112 | |||
| 113 | static inline int | ||
| 114 | xfs_filestream_put_ag( | ||
| 115 | xfs_mount_t *mp, | ||
| 116 | xfs_agnumber_t agno) | ||
| 117 | { | ||
| 118 | struct xfs_perag *pag; | ||
| 119 | int ret; | ||
| 120 | |||
| 121 | pag = xfs_perag_get(mp, agno); | ||
| 122 | ret = atomic_dec_return(&pag->pagf_fstrms); | ||
| 123 | xfs_perag_put(pag); | ||
| 124 | return ret; | ||
| 125 | } | ||
| 126 | |||
| 127 | /* allocation selection flags */ | 45 | /* allocation selection flags */ |
| 128 | typedef enum xfs_fstrm_alloc { | 46 | typedef enum xfs_fstrm_alloc { |
| 129 | XFS_PICK_USERDATA = 1, | 47 | XFS_PICK_USERDATA = 1, |
