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__ */ 137