cregit-Linux how code gets into the kernel

Release 4.12 include/uapi/linux/fsmap.h

 * FS_IOC_GETFSMAP ioctl infrastructure.
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <>
#ifndef _LINUX_FSMAP_H

#define _LINUX_FSMAP_H

#include <linux/types.h>

 *      Structure for FS_IOC_GETFSMAP.
 *      The memory layout for this call are the scalar values defined in
 *      struct fsmap_head, followed by two struct fsmap that describe
 *      the lower and upper bound of mappings to return, followed by an
 *      array of struct fsmap mappings.
 *      fmh_iflags control the output of the call, whereas fmh_oflags report
 *      on the overall record output.  fmh_count should be set to the
 *      length of the fmh_recs array, and fmh_entries will be set to the
 *      number of entries filled out during each call.  If fmh_count is
 *      zero, the number of reverse mappings will be returned in
 *      fmh_entries, though no mappings will be returned.  fmh_reserved
 *      must be set to zero.
 *      The two elements in the fmh_keys array are used to constrain the
 *      output.  The first element in the array should represent the
 *      lowest disk mapping ("low key") that the user wants to learn
 *      about.  If this value is all zeroes, the filesystem will return
 *      the first entry it knows about.  For a subsequent call, the
 *      contents of fsmap_head.fmh_recs[fsmap_head.fmh_count - 1] should be
 *      copied into fmh_keys[0] to have the kernel start where it left off.
 *      The second element in the fmh_keys array should represent the
 *      highest disk mapping ("high key") that the user wants to learn
 *      about.  If this value is all ones, the filesystem will not stop
 *      until it runs out of mapping to return or runs out of space in
 *      fmh_recs.
 *      fmr_device can be either a 32-bit cookie representing a device, or
 *      a 32-bit dev_t if the FMH_OF_DEV_T flag is set.  fmr_physical,
 *      fmr_offset, and fmr_length are expressed in units of bytes.
 *      fmr_owner is either an inode number, or a special value if
 *      FMR_OF_SPECIAL_OWNER is set in fmr_flags.

struct fsmap {
__u32		fmr_device;	/* device id */
__u32		fmr_flags;	/* mapping flags */
__u64		fmr_physical;	/* device offset of segment */
__u64		fmr_owner;	/* owner id */
__u64		fmr_offset;	/* file offset of segment */
__u64		fmr_length;	/* length of segment */
__u64		fmr_reserved[3];	/* must be zero */

struct fsmap_head {
__u32		fmh_iflags;	/* control flags */
__u32		fmh_oflags;	/* output flags */
__u32		fmh_count;	/* # of entries in array incl. input */
__u32		fmh_entries;	/* # of entries filled in (output). */
__u64		fmh_reserved[6];	/* must be zero */

struct fsmap	fmh_keys[2];	/* low and high keys for the mapping search */
struct fsmap	fmh_recs[];	/* returned records */

/* Size of an fsmap_head with room for nr records. */

static inline size_t fsmap_sizeof( unsigned int nr) { return sizeof(struct fsmap_head) + nr * sizeof(struct fsmap); }


Darrick J. Wong26100.00%1100.00%

/* Start the next fsmap query at the end of the current query results. */
static inline void fsmap_advance( struct fsmap_head *head) { head->fmh_keys[0] = head->fmh_recs[head->fmh_entries - 1]; }


Darrick J. Wong30100.00%1100.00%

/* fmh_iflags values - set by FS_IOC_GETFSMAP caller in the header. */ /* no flags defined yet */ #define FMH_IF_VALID 0 /* fmh_oflags values - returned in the header segment only. */ #define FMH_OF_DEV_T 0x1 /* fmr_device values will be dev_t */ /* fmr_flags values - returned for each non-header segment */ #define FMR_OF_PREALLOC 0x1 /* segment = unwritten pre-allocation */ #define FMR_OF_ATTR_FORK 0x2 /* segment = attribute fork */ #define FMR_OF_EXTENT_MAP 0x4 /* segment = extent map */ #define FMR_OF_SHARED 0x8 /* segment = shared with another file */ #define FMR_OF_SPECIAL_OWNER 0x10 /* owner is a special value */ #define FMR_OF_LAST 0x20 /* segment is the last in the FS */ /* Each FS gets to define its own special owner codes. */ #define FMR_OWNER(type, code) (((__u64)type << 32) | \ ((__u64)code & 0xFFFFFFFFULL)) #define FMR_OWNER_TYPE(owner) ((__u32)((__u64)owner >> 32)) #define FMR_OWNER_CODE(owner) ((__u32)(((__u64)owner & 0xFFFFFFFFULL))) #define FMR_OWN_FREE FMR_OWNER(0, 1) /* free space */ #define FMR_OWN_UNKNOWN FMR_OWNER(0, 2) /* unknown owner */ #define FMR_OWN_METADATA FMR_OWNER(0, 3) /* metadata */ #define FS_IOC_GETFSMAP _IOWR('X', 59, struct fsmap_head) #endif /* _LINUX_FSMAP_H */

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Darrick J. Wong236100.00%1100.00%
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