--- /dev/null
+============
+Fiemap Ioctl
+============
+
+The fiemap ioctl is an efficient method for userspace to get file
+extent mappings. Instead of block-by-block mapping (such as bmap), fiemap
+returns a list of extents.
+
+
+Request Basics
+--------------
+
+A fiemap request is encoded within struct fiemap:
+
+struct fiemap {
+ __u64 fm_start; /* logical offset (inclusive) at
+ * which to start mapping (in) */
+ __u64 fm_length; /* logical length of mapping which
+ * userspace cares about (in) */
+ __u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
+ __u32 fm_mapped_extents; /* number of extents that were
+ * mapped (out) */
+ __u32 fm_extent_count; /* size of fm_extents array (in) */
+ __u32 fm_reserved;
+ struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
+};
+
+
+fm_start, and fm_length specify the logical range within the file
+which the process would like mappings for. Extents returned mirror
+those on disk - that is, the logical offset of the 1st returned extent
+may start before fm_start, and the range covered by the last returned
+extent may end after fm_length. All offsets and lengths are in bytes.
+
+Certain flags to modify the way in which mappings are looked up can be
+set in fm_flags. If the kernel doesn't understand some particular
+flags, it will return EBADR and the contents of fm_flags will contain
+the set of flags which caused the error. If the kernel is compatible
+with all flags passed, the contents of fm_flags will be unmodified.
+It is up to userspace to determine whether rejection of a particular
+flag is fatal to it's operation. This scheme is intended to allow the
+fiemap interface to grow in the future but without losing
+compatibility with old software.
+
+fm_extent_count specifies the number of elements in the fm_extents[] array
+that can be used to return extents. If fm_extent_count is zero, then the
+fm_extents[] array is ignored (no extents will be returned), and the
+fm_mapped_extents count will hold the number of extents needed in
+fm_extents[] to hold the file's current mapping. Note that there is
+nothing to prevent the file from changing between calls to FIEMAP.
+
+The following flags can be set in fm_flags:
+
+* FIEMAP_FLAG_SYNC
+If this flag is set, the kernel will sync the file before mapping extents.
+
+* FIEMAP_FLAG_XATTR
+If this flag is set, the extents returned will describe the inodes
+extended attribute lookup tree, instead of it's data tree.
+
+
+Extent Mapping
+--------------
+
+Extent information is returned within the embedded fm_extents array
+which userspace must allocate along with the fiemap structure. The
+number of elements in the fiemap_extents[] array should be passed via
+fm_extent_count. The number of extents mapped by kernel will be
+returned via fm_mapped_extents. If the number of fiemap_extents
+allocated is less than would be required to map the requested range,
+the maximum number of extents that can be mapped in the fm_extent[]
+array will be returned and fm_mapped_extents will be equal to
+fm_extent_count. In that case, the last extent in the array will not
+complete the requested range and will not have the FIEMAP_EXTENT_LAST
+flag set (see the next section on extent flags).
+
+Each extent is described by a single fiemap_extent structure as
+returned in fm_extents.
+
+struct fiemap_extent {
+ __u64 fe_logical; /* logical offset in bytes for the start of
+ * the extent */
+ __u64 fe_physical; /* physical offset in bytes for the start
+ * of the extent */
+ __u64 fe_length; /* length in bytes for the extent */
+ __u64 fe_reserved64[2];
+ __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
+ __u32 fe_reserved[3];
+};
+
+All offsets and lengths are in bytes and mirror those on disk. It is valid
+for an extents logical offset to start before the request or it's logical
+length to extend past the request. Unless FIEMAP_EXTENT_NOT_ALIGNED is
+returned, fe_logical, fe_physical, and fe_length will be aligned to the
+block size of the file system. With the exception of extents flagged as
+FIEMAP_EXTENT_MERGED, adjacent extents will not be merged.
+
+The fe_flags field contains flags which describe the extent returned.
+A special flag, FIEMAP_EXTENT_LAST is always set on the last extent in
+the file so that the process making fiemap calls can determine when no
+more extents are available, without having to call the ioctl again.
+
+Some flags are intentionally vague and will always be set in the
+presence of other more specific flags. This way a program looking for
+a general property does not have to know all existing and future flags
+which imply that property.
+
+For example, if FIEMAP_EXTENT_DATA_INLINE or FIEMAP_EXTENT_DATA_TAIL
+are set, FIEMAP_EXTENT_NOT_ALIGNED will also be set. A program looking
+for inline or tail-packed data can key on the specific flag. Software
+which simply cares not to try operating on non-aligned extents
+however, can just key on FIEMAP_EXTENT_NOT_ALIGNED, and not have to
+worry about all present and future flags which might imply unaligned
+data. Note that the opposite is not true - it would be valid for
+FIEMAP_EXTENT_NOT_ALIGNED to appear alone.
+
+* FIEMAP_EXTENT_LAST
+This is the last extent in the file. A mapping attempt past this
+extent will return nothing.
+
+* FIEMAP_EXTENT_UNKNOWN
+The location of this extent is currently unknown. This may indicate
+the data is stored on an inaccessible volume or that no storage has
+been allocated for the file yet.
+
+* FIEMAP_EXTENT_DELALLOC
+ - This will also set FIEMAP_EXTENT_UNKNOWN.
+Delayed allocation - while there is data for this extent, it's
+physical location has not been allocated yet.
+
+* FIEMAP_EXTENT_ENCODED
+This extent does not consist of plain filesystem blocks but is
+encoded (e.g. encrypted or compressed). Reading the data in this
+extent via I/O to the block device will have undefined results.
+
+Note that it is *always* undefined to try to update the data
+in-place by writing to the indicated location without the
+assistance of the filesystem, or to access the data using the
+information returned by the FIEMAP interface while the filesystem
+is mounted. In other words, user applications may only read the
+extent data via I/O to the block device while the filesystem is
+unmounted, and then only if the FIEMAP_EXTENT_ENCODED flag is
+clear; user applications must not try reading or writing to the
+filesystem via the block device under any other circumstances.
+
+* FIEMAP_EXTENT_DATA_ENCRYPTED
+ - This will also set FIEMAP_EXTENT_ENCODED
+The data in this extent has been encrypted by the file system.
+
+* FIEMAP_EXTENT_NOT_ALIGNED
+Extent offsets and length are not guaranteed to be block aligned.
+
+* FIEMAP_EXTENT_DATA_INLINE
+ This will also set FIEMAP_EXTENT_NOT_ALIGNED
+Data is located within a meta data block.
+
+* FIEMAP_EXTENT_DATA_TAIL
+ This will also set FIEMAP_EXTENT_NOT_ALIGNED
+Data is packed into a block with data from other files.
+
+* FIEMAP_EXTENT_UNWRITTEN
+Unwritten extent - the extent is allocated but it's data has not been
+initialized. This indicates the extent's data will be all zero if read
+through the filesystem but the contents are undefined if read directly from
+the device.
+
+* FIEMAP_EXTENT_MERGED
+This will be set when a file does not support extents, i.e., it uses a block
+based addressing scheme. Since returning an extent for each block back to
+userspace would be highly inefficient, the kernel will try to merge most
+adjacent blocks into 'extents'.
+
+
+VFS -> File System Implementation
+---------------------------------
+
+File systems wishing to support fiemap must implement a ->fiemap callback on
+their inode_operations structure. The fs ->fiemap call is responsible for
+defining it's set of supported fiemap flags, and calling a helper function on
+each discovered extent:
+
+struct inode_operations {
+ ...
+
+ int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
+ u64 len);
+
+->fiemap is passed struct fiemap_extent_info which describes the
+fiemap request:
+
+struct fiemap_extent_info {
+ unsigned int fi_flags; /* Flags as passed from user */
+ unsigned int fi_extents_mapped; /* Number of mapped extents */
+ unsigned int fi_extents_max; /* Size of fiemap_extent array */
+ struct fiemap_extent *fi_extents_start; /* Start of fiemap_extent array */
+};
+
+It is intended that the file system should not need to access any of this
+structure directly.
+
+
+Flag checking should be done at the beginning of the ->fiemap callback via the
+fiemap_check_flags() helper:
+
+int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
+
+The struct fieinfo should be passed in as recieved from ioctl_fiemap(). The
+set of fiemap flags which the fs understands should be passed via fs_flags. If
+fiemap_check_flags finds invalid user flags, it will place the bad values in
+fieinfo->fi_flags and return -EBADR. If the file system gets -EBADR, from
+fiemap_check_flags(), it should immediately exit, returning that error back to
+ioctl_fiemap().
+
+
+For each extent in the request range, the file system should call
+the helper function, fiemap_fill_next_extent():
+
+int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
+ u64 phys, u64 len, u32 flags, u32 dev);
+
+fiemap_fill_next_extent() will use the passed values to populate the
+next free extent in the fm_extents array. 'General' extent flags will
+automatically be set from specific flags on behalf of the calling file
+system so that the userspace API is not broken.
+
+fiemap_fill_next_extent() returns 0 on success, and 1 when the
+user-supplied fm_extents array is full. If an error is encountered
+while copying the extent to user memory, -EFAULT will be returned.
#include <asm/ioctls.h>
+/* So that the fiemap access checks can't overflow on 32 bit machines. */
+#define FIEMAP_MAX_EXTENTS (UINT_MAX / sizeof(struct fiemap_extent))
+
/**
* vfs_ioctl - call filesystem specific ioctl methods
* @filp: open file to invoke ioctl method on
return put_user(res, p);
}
+/**
+ * fiemap_fill_next_extent - Fiemap helper function
+ * @fieinfo: Fiemap context passed into ->fiemap
+ * @logical: Extent logical start offset, in bytes
+ * @phys: Extent physical start offset, in bytes
+ * @len: Extent length, in bytes
+ * @flags: FIEMAP_EXTENT flags that describe this extent
+ *
+ * Called from file system ->fiemap callback. Will populate extent
+ * info as passed in via arguments and copy to user memory. On
+ * success, extent count on fieinfo is incremented.
+ *
+ * Returns 0 on success, -errno on error, 1 if this was the last
+ * extent that will fit in user array.
+ */
+#define SET_UNKNOWN_FLAGS (FIEMAP_EXTENT_DELALLOC)
+#define SET_NO_UNMOUNTED_IO_FLAGS (FIEMAP_EXTENT_DATA_ENCRYPTED)
+#define SET_NOT_ALIGNED_FLAGS (FIEMAP_EXTENT_DATA_TAIL|FIEMAP_EXTENT_DATA_INLINE)
+int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical,
+ u64 phys, u64 len, u32 flags)
+{
+ struct fiemap_extent extent;
+ struct fiemap_extent *dest = fieinfo->fi_extents_start;
+
+ /* only count the extents */
+ if (fieinfo->fi_extents_max == 0) {
+ fieinfo->fi_extents_mapped++;
+ return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
+ }
+
+ if (fieinfo->fi_extents_mapped >= fieinfo->fi_extents_max)
+ return 1;
+
+ if (flags & SET_UNKNOWN_FLAGS)
+ flags |= FIEMAP_EXTENT_UNKNOWN;
+ if (flags & SET_NO_UNMOUNTED_IO_FLAGS)
+ flags |= FIEMAP_EXTENT_ENCODED;
+ if (flags & SET_NOT_ALIGNED_FLAGS)
+ flags |= FIEMAP_EXTENT_NOT_ALIGNED;
+
+ memset(&extent, 0, sizeof(extent));
+ extent.fe_logical = logical;
+ extent.fe_physical = phys;
+ extent.fe_length = len;
+ extent.fe_flags = flags;
+
+ dest += fieinfo->fi_extents_mapped;
+ if (copy_to_user(dest, &extent, sizeof(extent)))
+ return -EFAULT;
+
+ fieinfo->fi_extents_mapped++;
+ if (fieinfo->fi_extents_mapped == fieinfo->fi_extents_max)
+ return 1;
+ return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
+}
+EXPORT_SYMBOL(fiemap_fill_next_extent);
+
+/**
+ * fiemap_check_flags - check validity of requested flags for fiemap
+ * @fieinfo: Fiemap context passed into ->fiemap
+ * @fs_flags: Set of fiemap flags that the file system understands
+ *
+ * Called from file system ->fiemap callback. This will compute the
+ * intersection of valid fiemap flags and those that the fs supports. That
+ * value is then compared against the user supplied flags. In case of bad user
+ * flags, the invalid values will be written into the fieinfo structure, and
+ * -EBADR is returned, which tells ioctl_fiemap() to return those values to
+ * userspace. For this reason, a return code of -EBADR should be preserved.
+ *
+ * Returns 0 on success, -EBADR on bad flags.
+ */
+int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags)
+{
+ u32 incompat_flags;
+
+ incompat_flags = fieinfo->fi_flags & ~(FIEMAP_FLAGS_COMPAT & fs_flags);
+ if (incompat_flags) {
+ fieinfo->fi_flags = incompat_flags;
+ return -EBADR;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(fiemap_check_flags);
+
+static int fiemap_check_ranges(struct super_block *sb,
+ u64 start, u64 len, u64 *new_len)
+{
+ *new_len = len;
+
+ if (len == 0)
+ return -EINVAL;
+
+ if (start > sb->s_maxbytes)
+ return -EFBIG;
+
+ /*
+ * Shrink request scope to what the fs can actually handle.
+ */
+ if ((len > sb->s_maxbytes) ||
+ (sb->s_maxbytes - len) < start)
+ *new_len = sb->s_maxbytes - start;
+
+ return 0;
+}
+
+static int ioctl_fiemap(struct file *filp, unsigned long arg)
+{
+ struct fiemap fiemap;
+ struct fiemap_extent_info fieinfo = { 0, };
+ struct inode *inode = filp->f_path.dentry->d_inode;
+ struct super_block *sb = inode->i_sb;
+ u64 len;
+ int error;
+
+ if (!inode->i_op->fiemap)
+ return -EOPNOTSUPP;
+
+ if (copy_from_user(&fiemap, (struct fiemap __user *)arg,
+ sizeof(struct fiemap)))
+ return -EFAULT;
+
+ if (fiemap.fm_extent_count > FIEMAP_MAX_EXTENTS)
+ return -EINVAL;
+
+ error = fiemap_check_ranges(sb, fiemap.fm_start, fiemap.fm_length,
+ &len);
+ if (error)
+ return error;
+
+ fieinfo.fi_flags = fiemap.fm_flags;
+ fieinfo.fi_extents_max = fiemap.fm_extent_count;
+ fieinfo.fi_extents_start = (struct fiemap_extent *)(arg + sizeof(fiemap));
+
+ if (fiemap.fm_extent_count != 0 &&
+ !access_ok(VERIFY_WRITE, fieinfo.fi_extents_start,
+ fieinfo.fi_extents_max * sizeof(struct fiemap_extent)))
+ return -EFAULT;
+
+ if (fieinfo.fi_flags & FIEMAP_FLAG_SYNC)
+ filemap_write_and_wait(inode->i_mapping);
+
+ error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start, len);
+ fiemap.fm_flags = fieinfo.fi_flags;
+ fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;
+ if (copy_to_user((char *)arg, &fiemap, sizeof(fiemap)))
+ error = -EFAULT;
+
+ return error;
+}
+
static int file_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
switch (cmd) {
case FIBMAP:
return ioctl_fibmap(filp, p);
+ case FS_IOC_FIEMAP:
+ return ioctl_fiemap(filp, arg);
case FIGETBSZ:
return put_user(inode->i_sb->s_blocksize, p);
case FIONREAD:
--- /dev/null
+/*
+ * FS_IOC_FIEMAP ioctl infrastructure.
+ *
+ * Some portions copyright (C) 2007 Cluster File Systems, Inc
+ *
+ * Authors: Mark Fasheh <mfasheh@suse.com>
+ * Kalpak Shah <kalpak.shah@sun.com>
+ * Andreas Dilger <adilger@sun.com>
+ */
+
+#ifndef _LINUX_FIEMAP_H
+#define _LINUX_FIEMAP_H
+
+struct fiemap_extent {
+ __u64 fe_logical; /* logical offset in bytes for the start of
+ * the extent from the beginning of the file */
+ __u64 fe_physical; /* physical offset in bytes for the start
+ * of the extent from the beginning of the disk */
+ __u64 fe_length; /* length in bytes for this extent */
+ __u64 fe_reserved64[2];
+ __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
+ __u32 fe_reserved[3];
+};
+
+struct fiemap {
+ __u64 fm_start; /* logical offset (inclusive) at
+ * which to start mapping (in) */
+ __u64 fm_length; /* logical length of mapping which
+ * userspace wants (in) */
+ __u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
+ __u32 fm_mapped_extents;/* number of extents that were mapped (out) */
+ __u32 fm_extent_count; /* size of fm_extents array (in) */
+ __u32 fm_reserved;
+ struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
+};
+
+#define FIEMAP_MAX_OFFSET (~0ULL)
+
+#define FIEMAP_FLAG_SYNC 0x00000001 /* sync file data before map */
+#define FIEMAP_FLAG_XATTR 0x00000002 /* map extended attribute tree */
+
+#define FIEMAP_FLAGS_COMPAT (FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR)
+
+#define FIEMAP_EXTENT_LAST 0x00000001 /* Last extent in file. */
+#define FIEMAP_EXTENT_UNKNOWN 0x00000002 /* Data location unknown. */
+#define FIEMAP_EXTENT_DELALLOC 0x00000004 /* Location still pending.
+ * Sets EXTENT_UNKNOWN. */
+#define FIEMAP_EXTENT_ENCODED 0x00000008 /* Data can not be read
+ * while fs is unmounted */
+#define FIEMAP_EXTENT_DATA_ENCRYPTED 0x00000080 /* Data is encrypted by fs.
+ * Sets EXTENT_NO_BYPASS. */
+#define FIEMAP_EXTENT_NOT_ALIGNED 0x00000100 /* Extent offsets may not be
+ * block aligned. */
+#define FIEMAP_EXTENT_DATA_INLINE 0x00000200 /* Data mixed with metadata.
+ * Sets EXTENT_NOT_ALIGNED.*/
+#define FIEMAP_EXTENT_DATA_TAIL 0x00000400 /* Multiple files in block.
+ * Sets EXTENT_NOT_ALIGNED.*/
+#define FIEMAP_EXTENT_UNWRITTEN 0x00000800 /* Space allocated, but
+ * no data (i.e. zero). */
+#define FIEMAP_EXTENT_MERGED 0x00001000 /* File does not natively
+ * support extents. Result
+ * merged for efficiency. */
+
+#endif /* _LINUX_FIEMAP_H */
#define FS_IOC_SETFLAGS _IOW('f', 2, long)
#define FS_IOC_GETVERSION _IOR('v', 1, long)
#define FS_IOC_SETVERSION _IOW('v', 2, long)
+#define FS_IOC_FIEMAP _IOWR('f', 11, struct fiemap)
#define FS_IOC32_GETFLAGS _IOR('f', 1, int)
#define FS_IOC32_SETFLAGS _IOW('f', 2, int)
#define FS_IOC32_GETVERSION _IOR('v', 1, int)
#include <linux/mutex.h>
#include <linux/capability.h>
#include <linux/semaphore.h>
+#include <linux/fiemap.h>
#include <asm/atomic.h>
#include <asm/byteorder.h>
*/
extern int file_permission(struct file *, int);
+/*
+ * VFS FS_IOC_FIEMAP helper definitions.
+ */
+struct fiemap_extent_info {
+ unsigned int fi_flags; /* Flags as passed from user */
+ unsigned int fi_extents_mapped; /* Number of mapped extents */
+ unsigned int fi_extents_max; /* Size of fiemap_extent array */
+ struct fiemap_extent *fi_extents_start; /* Start of fiemap_extent
+ * array */
+};
+int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
+ u64 phys, u64 len, u32 flags);
+int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
+
/*
* File types
*
void (*truncate_range)(struct inode *, loff_t, loff_t);
long (*fallocate)(struct inode *inode, int mode, loff_t offset,
loff_t len);
+ int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
+ u64 len);
};
struct seq_file;
projects / openwrt / staging / blogic.git / commitdiff