source: gpfs_3.1_ker2.6.20/lpp/mmfs/include/gpfs_fcntl.h @ 195

/* IBM_PROLOG_BEGIN_TAG                                                   */
/* This is an automatically generated prolog.                             */
/*                                                                        */
/*                                                                        */
/*                                                                        */
/* Licensed Materials - Property of IBM                                   */
/*                                                                        */
/* Restricted Materials of IBM                                            */
/*                                                                        */
/* (C) COPYRIGHT International Business Machines Corp. 1999,2006          */
/* All Rights Reserved                                                    */
/*                                                                        */
/* US Government Users Restricted Rights - Use, duplication or            */
/* disclosure restricted by GSA ADP Schedule Contract with IBM Corp.      */
/*                                                                        */
/* IBM_PROLOG_END_TAG                                                     */
/* @(#)51       1.14  src/avs/fs/mmfs/ts/kernext/gpfs_fcntl.h, mmfs, avs_rgpfs24, rgpfs24s001a 3/24/06 19:37:40 */

/*
 * GPFS interface definitions for supporting I/O hints and directives.
 *
 * Usage: The argument to gpfs_fcntl is composed of the concatenation of
 * structures defined in this file.  The first structure must be of type
 * gpfsFcntlHeader_t.  This is immediately followed by additional
 * structures, one for each hint or directive supplied.  The totalLength
 * field of the header contains the length of all of the structures,
 * including the header itself.  Each structure is defined to be a multiple
 * of 8 bytes in length, and the highest alignment requirement of any of the
 * data types is also 8 bytes, so the compiler will not insert padding when
 * several structures are declared within an outer structure.  This makes
 * it easier to build up the necessary area before calling gpfs_fcntl.
 *
 * For example, the following code fragment first releases all cached data
 * held on behalf of a file, then tells GPFS that this node will write
 * the portion of the file with file offsets between 2G and 3G-1:
 *   struct
 *   {
 *     gpfsFcntlHeader_t hdr;
 *     gpfsClearFileCache_t rel;
 *     gpfsAccessRange_t acc;
 *   } arg;
 *
 *   arg.hdr.totalLength = sizeof(arg);
 *   arg.hdr.fcntlVersion = GPFS_FCNTL_CURRENT_VERSION;
 *   arg.hdr.fcntlReserved = 0;
 *   arg.rel.structLen = sizeof(arg.rel);
 *   arg.rel.structType = GPFS_CLEAR_FILE_CACHE;
 *   arg.acc.structLen = sizeof(arg.acc);
 *   arg.acc.structType = GPFS_ACCESS_RANGE;
 *   arg.acc.start = 2LL * 1024LL * 1024LL * 1024LL;
 *   arg.acc.length = 1024 * 1024 * 1024;
 *   arg.acc.isWrite = 1;
 *   rc = gpfs_fcntl(handle, &arg);
 *
 * If gpfs_fcntl returns an error (rc -1), errno will contain the error
 * reason, and the errorOffset field of the header will contain the offset
 * of the offending structure within the argument area.
 *
 * In general, the structures within the argument are processed in order,
 * except that data shipping directives are performed after all other hints
 * and directives.
 */

#ifndef _h_gpfs_fcntl
#define _h_gpfs_fcntl

/* Header of the parameter area passed to gpfs_fcntl */
typedef struct
{
  int           totalLength;    /* length of this structure plus the sum of
                                   the lengths of all structures in this
                                   gpfs_fcntl argument */
  int           fcntlVersion;   /* version number: GPFS_FCNTL_CURRENT_VERSION */
  int           errorOffset;    /* Returned value giving offset into parameter
                                   area of the structure to which errno
                                   pertains.  Only set if errno is set. */
  int           fcntlReserved;  /* not used, should be set to 0 */
} gpfsFcntlHeader_t;


/* Interface version number (fcntlVersion field of gpfsFcntlHeader_t) */
#define GPFS_FCNTL_CURRENT_VERSION      1

/* Maximum length of argument to gpfs_fcntl */
#define GPFS_MAX_FCNTL_LENGTH       65536

/* Maximum length of a name arguement passed to or returned from gpfs_fcntl.
   Length of buffer must be a multiple of 8. */
#define GPFS_FCNTL_MAX_NAME_BUFFER  256 
#define GPFS_FCNTL_MIN_NAME_BUFFER  8


/* Definitions of structType fields for GPFS hints.  Hints can be ignored
   by GPFS without affecting correct operation, although performance might
   suffer. */
#define GPFS_ACCESS_RANGE            1001
#define GPFS_FREE_RANGE              1002
#define GPFS_MULTIPLE_ACCESS_RANGE   1003
#define GPFS_CLEAR_FILE_CACHE        1004

/* Definitions of structType fields for GPFS directives.  GPFS must honor
   directives, or return an error saying why a directive could not be
   honored. */
#define GPFS_CANCEL_HINTS            2001
#define GPFS_DATA_SHIP_START         2002
#define GPFS_DATA_SHIP_MAP           2003
#define GPFS_DATA_SHIP_STOP          2004
#define GPFS_FCNTL_SET_REPLICATION   2005
#define GPFS_FCNTL_SET_STORAGEPOOL   2006
#define GPFS_FCNTL_RESTRIPE_DATA     2007


/* Definitions of structType fileds for GPFS inquiries. Inquiries merely
   return GPFS attributes of existing files. */
#define GPFS_FCNTL_GET_REPLICATION   3001
#define GPFS_FCNTL_GET_STORAGEPOOL   3002
#define GPFS_FCNTL_GET_FILESETNAME   3003
#define GPFS_FCNTL_GET_SNAPSHOTNAME  3004



/* Structures for specifying the various gpfs_fnctl hints */

/* Access range hint:  The application will soon access file offsets within
   the given range, and will not access offsets outside the range.  Violating
   this hint may produce worse performance than if no hint was specified. */
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* hint identifier: GPFS_ACCESS_RANGE */
  long long     start;          /* start offset in bytes from beginning of file */
  long long     length;         /* length of range; 0 indicates to end of file */
  int           isWrite;        /* 0 - read access, 1 - write access */
  char          padding[4];
} gpfsAccessRange_t;


/* Free range hint: the application will no longer access file offsets
   within the given range, so GPFS is free to flush those file offsets from
   its cache. */
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* hint identifier: GPFS_FREE_RANGE */
  long long     start;          /* start offset in bytes from beginning of file */
  long long     length;         /* length of range; 0 indicates to end of file */
} gpfsFreeRange_t;


/* Format of accRangeArray and relRangeArray entries used by
   GPFS_MULTIPLE_ACCESS_RANGE hint */
typedef struct
{
  long long     blockNumber;    /* data block number to access */
  int           start;          /* start of range (from beginning of block) */
  int           length;         /* number of bytes in the range  */
  int           isWrite;        /* 0 - read access, 1 - write access */
  char          padding[4];
} gpfsRangeArray_t;

/* Multiple access range hint: This hint is used to drive application-defined
   prefetching and writebehind.  The application will soon access the
   portions of the blocks specified in accRangeArray, and has finished
   accessing the ranges listed in relRangeArray.  The size of a block is
   returned by stat in the st_blksize field, so offset OFF of a file is in
   block OFF/st_blksize.  Up to GPFS_MAX_RANGE_COUNT blocks may be given in
   one multiple access range hint.  Depending on the current load, GPFS may
   initiate prefetching of some or all of these.  Each range named in
   accRangeArray that is accepted for prefetching should eventually be
   released via relRangeArray, or else GPFS will stop prefetching blocks
   for this file. */
#define GPFS_MAX_RANGE_COUNT 8
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* hint identifier: GPFS_MULTIPLE_ACCESS_RANGE */
  int           accRangeCnt;    /* on input, number of ranges in accRangeArray
                                   on output, number of processed ranges (the
                                   first n of the given ranges) */
  int           relRangeCnt;    /* number of ranges in relRangeArray */
  gpfsRangeArray_t accRangeArray[GPFS_MAX_RANGE_COUNT]; /* requested ranges */
  gpfsRangeArray_t relRangeArray[GPFS_MAX_RANGE_COUNT]; /* ranges to release */
} gpfsMultipleAccessRange_t;


/* Clear file cache hint: the application expects to no longer access any
   portion of the file, so GPFS should flush and invalidate any cached
   data belonging to this file.  This may avoid synchronous cache invalidations
   on later uses of the file by other nodes. */
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* hint identifier: GPFS_CLEAR_FILE_CACHE */
} gpfsClearFileCache_t;



/* Structures for specifying the various gpfs_fnctl directives */

/* Cancel all hints: GPFS removes any hints that may have been issued
   against this file.  Does not affect the contents of the GPFS file cache.
   Note that this directive does not cancel the effect of other directives,
   such as GPFS_DATA_SHIP_START. */
typedef struct  /* cancelAccessHints hint */
{
  int           structLen;      /* length of this structure */
  int           structType;     /* hint identifier: GPFS_CANCEL_HINTS */
} gpfsCancelHints_t;


/* Initiate data shipping mode: once all participating threads have issued
   this hint for a file, GPFS enters a mode where it partitions the blocks
   of the file among a group of agent nodes.  In data shipping mode, all
   file accesses result in GPFS messages to the appropriate agent(s) to read
   or write the requested data.  Applications that perform fine-grained
   write sharing should benefit most from data shipping, since GPFS cache
   invalidations will be avoided.  Because an application level read or
   write may be split across several agents, Posix read/write file atomicity
   is not enforced while in data shipping mode. */
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* directive identifier: GPFS_DATA_SHIP_START */
  int           numInstances;   /* number of open file instances collaborating
                                   to operate on the file.  These may be on
                                   any number of nodes. */
  int           reserved;       /* not used, should be set to 0 */
} gpfsDataShipStart_t;


/* Specify the agent mapping for data shipping: tells GPFS which agent
   nodes to use for data shipping.  This directive can only appear in a
   gpfs_fcntl call that also gives the GPFS_DATA_SHIP_START directive.  If
   this directive is not used, the agents will be exactly the nodes on which
   the GPFS_DATA_SHIP_START directive was given, and the partition will be a
   round-robin distribution of the blocks of the file to the agent nodes.
   There are two forms of this directive.  The gpfsDataShipMap_t structure
   contains enough room for up to GPFS_MAX_DS_AGENT_NODES agent nodes.  If
   this is insufficient, the variable-size structure gpfsDataShipMapVariable_t
   may be used instead.  GPFS will infer the actual size of the agentNodeNumber
   array in the gpfsDataShipMapVariable_t structure from its structLen
   field.  To build the argument to gpfs_fcntl when gpfsDataShipMapVariable_t
   is used, the application needs to dynamically allocate space for all of
   the contiguous structures to be passed to gpfs_fcntl.  The following code
   fragment illustrates how this might be done:

     char * p;
     gpfsFcntlHeader_t * hdrP;
     gpfsDataShipStart_t * startP;
     gpfsDataShipMapVariable_t * mapP;
     int mapSize = GPFS_DATA_SHIP_MAP_VARIABLE_SIZE(nAgents);

     p = malloc(sizeof(gpfsFcntlHeader_t) + sizeof(gpfsDataShipStart_t) + mapSize);
     hdrP = (gpfsFcntlHeader_t *) p;
     startP = (gpfsDataShipStart_t *) (p + sizeof(gpfsFcntlHeader_t));
     mapP = (gpfsDataShipMapVariable_t *) (p + sizeof(gpfsFcntlHeader_t) +
                                           sizeof(gpfsDataShipStart_t));
     hdrP->totalLength = sizeof(gpfsFcntlHeader_t) +
                         sizeof(gpfsDataShipStart_t) + mapSize;
     ... fill in other fields in *hdrP
     startP->structLen = sizeof(gpfsDataShipStart_t);
     ... fill in other fields in *startP
     mapP->structLen = mapSize;
     ... fill in other fields in mapP, including nAgents entries in the
       mapP->agentNodeNumber array
     rc = gpfs_fcntl(handle, hdrP);
     free(p);

  As the example code shows, using gpfsDataShipMapVariable_t is more awkward
  than using gpfsDataShipMap_t, since the latter can simply be embedded
  within a larger structure that contains the necessary gpfsFcntlHeader_t
  and gpfsDataShipStart_t structures. */
#define GPFS_MAX_DS_AGENT_NODES 2048
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* directive identifier: GPFS_DATA_SHIP_MAP */
  int           partitionSize;  /* number of contiguous bytes per server */
  int           agentCount;     /* number of entries used in the
                                   agentNodeNumber array */
  int           agentNodeNumber[GPFS_MAX_DS_AGENT_NODES]; 
                                /* data ship agent node numbers, using 
                                   GPFS configuration data repository
                                   node numbers */
} gpfsDataShipMap_t;

typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* directive identifier: GPFS_DATA_SHIP_MAP */
  int           partitionSize;  /* number of contiguous bytes per server */
  int           agentCount;     /* number of entries used in the
                                   agentNodeNumber array */
  int           agentNodeNumber[2]; 
                                /* data ship agent node numbers, using 
                                   GPFS configuration data repository
                                   node numbers.  The actual size of this
                                   array will be inferred from structLen.
                                   The number of elements in the array must
                                   be even, so that the total structure size
                                   is a multiple of 8.  The number of
                                   entries used in the array is given by
                                   agentCount, and may be any positive value
                                   less than or equal to the size of the
                                   array. */
} gpfsDataShipMapVariable_t;

/* Compute the size in bytes of a gpfsDataShipMapVariable_t structure large
   enough to hold _nAgents data shipping agent node numbers */
#define GPFS_DATA_SHIP_MAP_VARIABLE_SIZE(_nAgents) \
  ( sizeof(gpfsDataShipMapVariable_t) - 2*sizeof(int) + \
    ((((_nAgents)+1)/2)*2)*sizeof(int) )


/* Terminate data shipping: waits for all threads that issued the
   GPFS_DATA_SHIP_START directive to issue this directive, then leaves data
   shipping mode. */
typedef struct
{
  int           structLen;      /* length of this structure */
  int           structType;     /* directive identifier: GPFS_DATA_SHIP_STOP */
} gpfsDataShipStop_t;


/* This directive is used to set a file's replication factors. 
   However, the directive does not cause the file data to be restriped 
   immediately. Instead the caller must append a gpfsRestripeData_t directive
   or invoke a mmrestripefs or a mmrestripefile command. */
typedef struct
{
  int structLen;               /* length of this structure */
  int structType;              /* directive identifier: 
                                  GPFS_FCNTL_SET_REPLICATION */
  int metadataReplicas;        /* Set the number of copies of the file's 
                                  indirect blocks. Valid values are 1 or 2,
                                  but not greater than the value of 
                                  maxMetadataReplicas. A value of 0 indicates
                                  not to change the current value. */  
  int maxMetadataReplicas;     /* Set the maximum number of copies of a file's
                                  indirect blocks. Space in the file's inode
                                  and indirect blocks is reserved for the
                                  maximum number of copies, regardless of the
                                  current value. Valid values are 1 or 2.
                                  A value of 0 indicates not to change the 
                                  current value. */
  int dataReplicas;            /* Set the number of copies of the file's
                                  data blocks. Valid values are 1 or 2,
                                  but cannot be greater than the value of
                                  maxDataReplicas. A value of 0 indicates
                                  not to change the current value. */
  int maxDataReplicas;         /* Set the maximum number of copies of a file's
                                  data blocks. Space in the file's inode
                                  and indirect blocks is reserved for the
                                  maximum number of copues, regardless of the
                                  current value. Valid values are 1 or 2. 
                                  A value of 0 indicates not the change the
                                  current value. */
  int errReason;               /* returned reason request failed.
                                  Defined below. */
  int errValue1;               /* returned value depending upon errReason */
  int errValue2;               /* returned value depending upon errReason */
  int reserved;                /* unused, but should be set to 0 */
} gpfsSetReplication_t;



/* Values that may be returned by errReason */

/* No reason information was returned. */
#define GPFS_FCNTL_ERR_NONE                       0

/* MetadataReplicas is out of range.
   errValue1 and errValue2 contain the valid lower and upper range boundaries. */
#define GPFS_FCNTL_ERR_METADATA_REPLICAS_RANGE    1

/* MaxMetadataReplicas is out of range.
   errValue1 and errValue2 contain the valid lower and upper range boundaries. */
#define GPFS_FCNTL_ERR_MAXMETADATA_REPLICAS_RANGE 2

/* DataReplicas is out of range.
   errValue1 and errValue2 contain the valid lower and upper range boundaries. */
#define GPFS_FCNTL_ERR_DATA_REPLICAS_RANGE        3

/* MaxDataReplicas is out of range.
   errValue1 and errValue2 contain the valid lower and upper range boundaries. */
#define GPFS_FCNTL_ERR_MAXDATA_REPLICAS_RANGE     4

/* An attempt to change maxMetadataReplicas or maxDataReplicas or both
   was made on a file that is not empty. */
#define GPFS_FCNTL_ERR_FILE_NOT_EMPTY             5

/* MetadataReplicas or dataReplicas or both exceed the number of failure groups.
   errValue1 contains the maximum number of metadata failure groups.
   errValue2 contains the maximum number of data failure groups. */
#define GPFS_FCNTL_ERR_REPLICAS_EXCEED_FGMAX      6



/* This directive is used to set a file's assigned storage pool. 
   However, the directive does not cause the file data to be migrated 
   immediately. Instead the caller must append a gpfsRestripeData_t 
   directive or invoke a mmrestripefs or mmrestripefile command. 
   The caller must have root privileges to change a file's storage pool. */
typedef struct
{
  int structLen;               /* length of this structure */
  int structType;              /* directive identifier: 
                                  GPFS_FCNTL_SET_STORAGEPOOL */
  int errReason;               /* returned reason request failed.
                                  Defined below. */
  int errValue1;               /* returned value depending upon errReason */
  int errValue2;               /* returned value depending upon errReason */
  int reserved;                /* unused, but should be set to 0 */
  char buffer[GPFS_FCNTL_MAX_NAME_BUFFER]; /* Null-terminated name of 
                                              storage pool to be assigned */
} gpfsSetStoragePool_t;


/* Values that may be returned by errReason */

/* Invalid storage pool name was given. */
#define GPFS_FCNTL_ERR_INVALID_STORAGE_POOL       7

/* Invalid storage pool. File cannot be assigned to given pool. */
#define GPFS_FCNTL_ERR_INVALID_STORAGE_POOL_TYPE  8

/* Invalid storage pool. Directories cannot be assigned to given pool. */
#define GPFS_FCNTL_ERR_INVALID_STORAGE_POOL_ISDIR 9

/* Invalid storage pool. System files cannot be assigned to given pool. */
#define GPFS_FCNTL_ERR_INVALID_STORAGE_POOL_ISLNK 10

/* Invalid storage pool. System files cannot be assigned to given pool. */
#define GPFS_FCNTL_ERR_INVALID_STORAGE_POOL_ISSYS 11

/* File system has not been upgraded to support storage pools */
#define GPFS_FCNTL_ERR_STORAGE_POOL_NOTENABLED    12

/* User does not have permission to perform the requested operation */
#define GPFS_FCNTL_ERR_NOPERM                     13




/* This directive is used to restripe a file's data blocks to update 
   its replication and/or migrate its data. The data movement is always 
   done immediately. */
typedef struct 
{
  int structLen;               /* length of this structure */
  int structType;              /* directive identifier: 
                                  GPFS_FCNTL_RESTRIPE_FILE */
  int options;                 /* options for restripe command. Defined below.
                                  See mmrestripefs command for details. */
  int errReason;               /* returned reason request failed.
                                  Defined below. */
  int errValue1;               /* returned value depending upon errReason */
  int errValue2;               /* returned value depending upon errReason */
  int reserved;                /* unused, but should be set to 0 */  
  int reserved2;               /* unused, but should be set to 0 */  
} gpfsRestripeData_t;


/* Define values for restripe options.
   See mmrestripefs command for complete definitions. */

/* Migrate critical data off of suspended disks. */
#define GPFS_FCNTL_RESTRIPE_M   0x0001

/* Replicate data against subsequent failure. */
#define GPFS_FCNTL_RESTRIPE_R   0x0002

/* Place file data in assigned storage pool. */
#define GPFS_FCNTL_RESTRIPE_P   0x0004

/* Rebalance file data */
#define GPFS_FCNTL_RESTRIPE_B   0x0008


/* Values that may be returned by errReason */

/* Not enough replicas could be created because the desired degree 
   of replication is larger than the number of failure groups. */
#define GPFS_FCNTL_ERR_NO_REPLICA_GROUP          14

/* Not enough replicas could be created because there was not 
   enough space left in one of the failure groups. */
#define GPFS_FCNTL_ERR_NO_REPLICA_SPACE          15

/* There was not enough space left on one of the disks to properly 
   balance the file according to the current stripe method. */
#define GPFS_FCNTL_ERR_NO_BALANCE_SPACE          16

/* The file could not be properly balanced because one or more 
   disks are unavailable. */
#define GPFS_FCNTL_ERR_NO_BALANCE_AVAILABLE      17

/* All replicas were on disks that have since been deleted 
   from the stripe group. */
#define GPFS_FCNTL_ERR_ADDR_BROKEN               18




/* Structures for specifying the various gpfs_fnctl inquiries.
   The inquiry directives may be used to obtain attributes of a files
   such as the file's replication factors, storage pool name, 
   fileset name or snapshot name. */

/* This inquiry is used to obtain a file's replication factors. */
typedef struct
 {
   int structLen;               /* length of this structure */
   int structType;              /* inquiry identifier: 
                                   GPFS_FCNTL_GET_REPLICATION */
   int metadataReplicas;        /* returns the current number of copies 
                                   of indirect blocks for the file. */
   int maxMetadataReplicas;     /* returns the maximum number of copies
                                   of indirect blocks for the file. */
   int dataReplicas;            /* returns the current number of copies
                                   of data blocks for the file. */
   int maxDataReplicas;         /* returns the maximum number of copies
                                   of data blocks for the file. */
   int status;                 /* returns the status of the file.
                                   Status values defined below. */
   int reserved;                /* unused, but should be set to 0 */
} gpfsGetReplication_t;


/* Flag definitions */

/* If set this file may have some data where the only replicas are 
   on suspended disks; implies some data may be lost if suspended
   disks are removed. */
#define GPFS_FCNTL_STATUS_EXPOSED        0x40000000

/* If set this file may not be properly replicated, i.e. some data 
   may have fewer or more than the desired number of replicas, 
   or some replicas may be on suspended disks. */
#define GPFS_FCNTL_STATUS_ILLREPLICATED  0x20000000

/* If set this file may not be properly balanced. */
#define GPFS_FCNTL_STATUS_UNBALANCED     0x10000000

/* If set this file has stale data blocks on at least one of the disks
   that are marked as unavailable or recovering in the stripe group 
   descriptor. */
#define GPFS_FCNTL_STATUS_DATAUPDATEMISS 0x08000000

/* If set this file has stale indirect blocks on at least one 
   unavailable or recovering disk. */
#define GPFS_FCNTL_STATUS_METAUPDATEMISS 0x04000000

/* If set this file may not be properly placed, i.e. some data may 
   be stored in an incorrect storage pool */
#define GPFS_FCNTL_STATUS_ILLPLACED      0x02000000



/* This inquiry is used to obtain the name of the storage assigned
   for the file's data. The size of the buffer may vary, but it must be 
   a multiple of 8. Upon successful completion of the call, the buffer 
   will contain a null-terminated character string for the name of the
   file's storage pool. */
typedef struct
{
  int structLen;               /* length of this structure */
  int structType;              /* inquiry identifier: 
                                   GPFS_FCNTL_GET_STORAGEPOOL */
  char buffer[GPFS_FCNTL_MAX_NAME_BUFFER]; /* returns with the file's
                                              storage pool name */
} gpfsGetStoragePool_t;


/* This inquiry is used to obtain the name of the fileset to which this 
   file has been assigned. The size of the buffer may vary, but it must be 
   a multiple of 8. Upon successful completion of the call, the buffer 
   will contain a null-terminated character string for the name of the
   file's fileset. */
typedef struct
{
   int structLen;               /* length of this structure */
   int structType;              /* inquiry identifier: 
                                   GPFS_FCNTL_GET_FILESETNAME */
  char buffer[GPFS_FCNTL_MAX_NAME_BUFFER]; /* returns with the file's
                                              fileset name */
} gpfsGetFilesetName_t;


/* This inquiry is used to obtain the name of the snapshot that includes 
   this file. If the file is not part of a snapshot, then a zero-length
   string will be returned. The size of the buffer may vary, but it must be 
   a multiple of 8. Upon successful completion of the call, the buffer 
   will contain a null-terminated character string for the name of the
   snapshot that includes this file. */
typedef struct {
   int structLen;               /* length of this structure */
   int structType;              /* inquiry identifier: 
                                   GPFS_FCNTL_GET_SNAPSHOTNAME */
  char buffer[GPFS_FCNTL_MAX_NAME_BUFFER]; /* returns with the file's
                                              snapshot name */
} gpfsGetSnapshotName_t;







/* NAME:        gpfs_fcntl()
 *
 * FUNCTION:    Pass hints and directives to GPFS on behalf of an open file
 *
 * Returns:      0      Successful
 *              -1      Failure
 *
 * Errno:       ENOSYS  Function not available
 *              EBADF   Bad file handle
 *              EINVAL  Not a GPFS file
 *              EINVAL  Not a regular file
 *              EINVAL  Ill-formed hint or directive
 *              E2BIG   Argument longer than GPFS_MAX_FCNTL_LENGTH
 */
#ifdef __cplusplus
extern "C"
{
#endif
int gpfs_fcntl(int fileDesc,            /* Open file descriptor */
                void* fcntlArgP);       /* argument list */
#ifdef __cplusplus
}
#endif

#endif /* _h_gpfs_fcntl */