FreeBSD/Linux Kernel Cross Reference
sys/geom/union/g_union.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2022 Marshall Kirk McKusick <mckusick@mckusick.com>
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #ifndef _G_UNION_H_
    #define _G_UNION_H_
    
    #define G_UNION_CLASS_NAME      "UNION"
    #define G_UNION_VERSION         1
    #define G_UNION_SUFFIX          ".union"
    /*
     * Special flag to instruct gunion to passthrough the underlying provider's
     * physical path
     */
    #define G_UNION_PHYSPATH_PASSTHROUGH "\255"
    
    #ifdef _KERNEL
    #define G_UNION_DEBUG(lvl, ...) \
        _GEOM_DEBUG("GEOM_UNION", g_union_debug, (lvl), NULL, __VA_ARGS__)
    #define G_UNION_LOGREQLVL(lvl, bp, ...) \
        _GEOM_DEBUG("GEOM_UNION", g_union_debug, (lvl), (bp), __VA_ARGS__)
    #define G_UNION_LOGREQ(bp, ...) G_UNION_LOGREQLVL(3, (bp), __VA_ARGS__)
    
    TAILQ_HEAD(wiplist, g_union_wip);
    
    /*
     * State maintained by each instance of a UNION GEOM.
     */
    struct g_union_softc {
            struct rwlock      sc_rwlock;           /* writemap lock */
            uint64_t         **sc_writemap_root;    /* root of write map */
            uint64_t          *sc_leafused;         /* 1 => leaf has allocation */
            uint64_t           sc_map_size;         /* size of write map */
            long               sc_root_size;        /* entries in root node */
            long               sc_leaf_size;        /* entries in leaf node */
            long               sc_bits_per_leaf;    /* bits per leaf node entry */
            long               sc_writemap_memory;  /* memory used by writemap */
            off_t              sc_offset;           /* starting offset in lower */
            off_t              sc_size;             /* size of union geom */
            off_t              sc_sectorsize;       /* sector size of geom */
            struct g_consumer *sc_uppercp;          /* upper-level provider */
            struct g_consumer *sc_lowercp;          /* lower-level provider */
            struct wiplist     sc_wiplist;          /* I/O work-in-progress list */
            long               sc_flags;            /* see flags below */
            long               sc_reads;            /* number of reads done */
            long               sc_wrotebytes;       /* number of bytes written */
            long               sc_writes;           /* number of writes done */
            long               sc_readbytes;        /* number of bytes read */
            long               sc_deletes;          /* number of deletes done */
            long               sc_getattrs;         /* number of getattrs done */
            long               sc_flushes;          /* number of flushes done */
            long               sc_cmd0s;            /* number of cmd0's done */
            long               sc_cmd1s;            /* number of cmd1's done */
            long               sc_cmd2s;            /* number of cmd2's done */
            long               sc_speedups;         /* number of speedups done */
            long               sc_readcurrentread;  /* reads current with read */
            long               sc_readblockwrite;   /* writes blocked by read */
            long               sc_writeblockread;   /* reads blocked by write */
            long               sc_writeblockwrite;  /* writes blocked by write */
    };
    
    /*
     * Structure to track work-in-progress I/O operations.
     *
     * Used to prevent overlapping I/O operations from running concurrently.
     * Created for each I/O operation.
     *
     * In usual case of no overlap it is linked to sc_wiplist and started.
     * If found to overlap an I/O on sc_wiplist, it is not started and is
     * linked to wip_waiting list of the I/O that it overlaps. When an I/O
     * completes, it restarts all the I/O operations on its wip_waiting list.
     */
    struct g_union_wip {
            struct wiplist           wip_waiting;   /* list of I/Os waiting on me */
            TAILQ_ENTRY(g_union_wip) wip_next;      /* pending or active I/O list */
            struct bio              *wip_bp;        /* bio for this I/O */
           struct g_union_softc    *wip_sc;        /* g_union's softc */
           off_t                    wip_start;     /* starting offset of I/O */
           off_t                    wip_end;       /* ending offset of I/O */
           long                     wip_numios;    /* BIO_READs in progress */
           long                     wip_error;     /* merged I/O errors */
   };
   
   /*
    * UNION flags
    */
   #define DOING_COMMIT    0x00000001      /* a commit command is in progress */
   
   #define DOING_COMMIT_BITNUM      0      /* a commit command is in progress */
   
   #define BITS_PER_ENTRY  (sizeof(uint64_t) * NBBY)
   #define G_RLOCK(sc)     rw_rlock(&(sc)->sc_rwlock)
   #define G_RUNLOCK(sc)   rw_runlock(&(sc)->sc_rwlock)
   #define G_WLOCK(sc)     rw_wlock(&(sc)->sc_rwlock)
   #define G_WUNLOCK(sc)   rw_wunlock(&(sc)->sc_rwlock)
   #define G_WLOCKOWNED(sc) rw_assert(&(sc)->sc_rwlock, RA_WLOCKED)
   
   /*
    * The writelock is held while a commit operation is in progress.
    * While held union device may not be used or in use.
    * Returns == 0 if lock was successfully obtained.
    */
   static inline int
   g_union_get_writelock(struct g_union_softc *sc)
   {
   
           return (atomic_testandset_long(&sc->sc_flags, DOING_COMMIT_BITNUM));
   }
   
   static inline void
   g_union_rel_writelock(struct g_union_softc *sc)
   {
           long ret __diagused;
   
           ret = atomic_testandclear_long(&sc->sc_flags, DOING_COMMIT_BITNUM);
           KASSERT(ret != 0, ("UNION GEOM releasing unheld lock"));
   }
   
   #endif  /* _KERNEL */
   
   #endif  /* _G_UNION_H_ */

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