The following functions operate on a filesystem handle. Most EXT2FS
Library functions require a filesystem handle as their first argument.
There are two functions which create a filesystem handle,
ext2fs_open and ext2fs_initialize.
The filesystem can also be closed using ext2fs_close, and any
changes to the superblock and group descripts can be written out to disk
using ext2fs_flush.
Most libext2fs functions take a filesystem handle of type
ext2_filsys. A filesystem handle is created either by opening
an existing function using ext2fs_open, or by initializing a new
filesystem using ext2fs_initialize.
Function: errcode_t ext2fs_open(const char *name, int flags, int superblock, int block_size, io_manager manager, ext2_filsys *ret_fs)
Opens a filesystem named name, using the the io_manager
manager to define the input/output routines needed to read and
write the filesystem. In the case of the unix_io io_manager,
name is interpreted as the Unix filename of the filesystem image.
This is often a device file, such as `/dev/hda1'.
The superblock parameter specifies the block number of the
superblock which should be used when opening the filesystem.
If superblock is zero, ext2fs_open will use the primary
superblock located at offset 1024 bytes from the start of the filesystem
image.
The block_size parameter specifies the block size used by the
filesystem. Normally this is determined automatically from the
filesystem uperblock. If block_size is non-zero, it must match
the block size found in the superblock, or the error
EXT2_ET_UNEXPECTED_BLOCK_SIZE will be returned. The
block_size parameter is also used to help fund the superblock when
superblock is non-zero.
The flags argument contains a bitmask of flags which control how
the filesystem open should be handled.
EXT2_FLAG_RW
Open the filesystem for reading and writing. Without this flag, the
filesystem is opened for reading only.
EXT2_FLAG_FORCE
Open the filesystem regardless of the feature sets listed in the
superblock.
Write any changes to the high-level filesystem data structures in the
fs filesystem. The following data structures will be written out:
The filesystem superblock
The filesystem group descriptors
The filesystem bitmaps, if read in via ext2fs_read_bitmaps.
Function: void ext2fs_free(ext2_filsys fs)
Close the io_manager abstraction for fs and release all memory
associated with the filesystem handle.
Function: errcode_t ext2fs_close(ext2_filsys fs)
Flush out any changes to the high-level filesystem data structures using
ext2fs_flush if the filesystem is marked dirty; then close and
free the filesystem using ext2fs_free.
An ext2 filesystem is initializing by the mke2fs program. The
two functions described here, ext2fs_initialize and
ext2fs_allocate_tables do much of the initial work for setting up
a filesystem. However, they don't do the whole job. mke2fs
calls ext2fs_initialize to set up the filesystem superblock, and
calls ext2fs_allocate_tables to allocate space for the inode
table, and the inode and block bitmaps. In addition, mke2fs must
also initialize the inode tables by clearing them with zeros, create the
root and lost+found directories, and reserve the reserved inodes.
This function is used by the mke2fs program to initialize a
filesystem. The ext2fs_initialize function creates a filesystem
handle which is returned in ret_fs that has been properly setup
for a filesystem to be located in name, using the io_manager
manager. The prototype superblock in param is used to
supply parameters such as the number of blocks in the filesystem, the
block size, etc.
The ext2fs_initialize function does not actually do any I/O; that
will be done when the application program calls ext2fs_close or
ext2fs_flush. Also, this function only initializes the
superblock and group descriptor structures. It does not create the
inode table or the root directory. This must be done by the calling
application, such as mke2fs.
The following values may be set in the param prototype superblock;
if a value of 0 is found in a field, ext2fs_initialize will use a
default value. The calling application should zero out the prototype
entire superblock, and then fill in any appropriate values.
s_blocks_count
The number of blocks in the filesystem. This parameter is mandatory and
must be set by the calling application.
s_inodes_count
The number of inodes in the filesystem. The
default value is determined by calculating the size of the filesystem,
and creating one inode for every 4096 bytes.
s_r_blocks_count
The number of blocks which should be reserved for the superuser. The
default value is zero blocks.
s_log_block_size
The blocksize of the filesystem. Valid values are 0 (1024 bytes), 1
(2048 bytes), or 2 (4096 bytes). The default blocksize is 1024 bytes.
s_log_frag_size
The size of fragments. The ext2 filesystem does not support fragments
(and may never support fragments). Currently this field must be the
same as s_log_block_size.
s_first_data_block
The first data block for the filesystem. For filesystem with a
blocksize of 1024 bytes, this value must be at least 1, since the
superblock is located in block number 1. For filesystems with larger
blocksizes, the superblock is still located at an offset of 1024 bytes,
so the superblock is located in block number 0. By default, this value
is set to 1 for filesystems with a block size of 1024 bytes, or 0 for
filesystems with larger blocksizes.
s_max_mnt_count
This field defines the number of times that the filesystem can be
mounted before it should be checked using e2fsck. When
e2fsck is run without the `-f' option, e2fsck will
skip the filesystem check if the number of times that the filesystem has
been mounted is less than s_max_mnt_count and if the interval
between the last time a filesystem check was performed and the current
time is less than s_checkinterval (see below). The default value
of s_max_mnt_count is 20.
s_checkinterval
This field defines the minimal interval between filesystem checks. See
the previous entry for a discussion of how this field is used by
e2fsck. The default value of this field is 180 days (six
months).
s_errors
This field defines the behavior which should be used by the kernel of
errors are detected in the filesystem. Possible values include:
Allocate space for the inode table and the block and inode bitmaps. The
inode tables and block and inode bitmaps aren't actually initialized;
this function just allocates the space for them.
The filesystem handle has a number of flags which can be manipulated
using the following function. Some of these flags affect how the
libext2fs filesystem behaves; others are provided solely for the
application's convenience.
Mark the filesystem fs as being dirty; this will cause
the superblock information to be flushed out when ext2fs_close is
called. ext2fs_mark_super_dirty will also set the filesystem
changed flag. The dirty flag is automatically cleared by
ext2fs_flush when the superblock is written to disk.
Function: int ext2fs_test_ib_dirty(ext2_filsys fs)
Function: int ext2fs_test_bb_dirty(ext2_filsys fs)
These flags indicate whether or not the inode or block bitmaps have been
modified. If the flag is set, it will cause the appropriate bitmap
to be written when the filesystem is closed or flushed.
The inode_scan abstraction is useful for iterating over all the inodes
in a filesystem.
Function: errcode_t ext2fs_open_inode_scan(ext2_filsys fs, int buffer_blocks, ext2_inode_scan *scan)
Initialize the iteration variable scan. This variable is used by
ext2fs_get_next_inode. The buffer_blocks parameter
controls how many blocks of the inode table are read in at a time. A
large number of blocks requires more memory, but reduces the overhead in
seeking and reading from the disk. If buffer_blocks is zero, a
suitable default value will be used.
Register a callback function which will be called by
ext2_get_next_inode when all of the inodes in a block group have
been processed.
Function: int ext2fs_inode_scan_flags(ext2_inode_scan scan, int set_flags, int clear_flags)
Set the scan_flags set_flags and clear the scan_flags clear_flags.
The following flags can be set using this interface:
`EXT2_SF_SKIP_MISSING_ITABLE'
When a block group is missing an inode table, skip it. If this flag is
not set ext2fs_get_next_inode will return the error
EXT2_ET_MISSING_INODE_TABLE.
ext2_ino_t ino, int flags, char *block_buf, int
(*func)(ext2_filsys fs, blk_t *blocknr, int blockcnt,
void *private), void *private)
Iterate over all of the blocks in inode number ino in filesystem
fs, by calling the function func for each block in the
inode. The block_buf parameter should either be NULL, or if the
ext2fs_block_iterate function is called repeatedly, the overhead
of allocating and freeing scratch memory can be avoided by passing a
pointer to a scratch buffer which must be at least as big as three times the
filesystem's blocksize.
The flags parameter controls how the iterator will function:
`BLOCK_FLAG_HOLE'
This flag indiciates that the interator function should be called on
blocks where the block number is zero (also known as "holes".) It is
also known as BLOCK_FLAG_APPEND, since it is also used by functions
such as ext2fs_expand_dir() to add a new block to an inode.
`BLOCK_FLAG_TRAVERSE'
This flag indicates that the iterator function for the
indirect, doubly indirect, etc. blocks should be called after all
of the blocks containined in the indirect blocks are processed.
This is useful if you are going to be deallocating blocks from an
inode.
`BLOCK_FLAG_DATA_ONLY'
This flag indicates that the iterator function should be
called for data blocks only.
The callback function func is called with a number of parameters;
the fs and private parameters are self-explanatory, and
their values are taken from the parameters to
ext2fs_block_iterate. (The private data structure is
generally used by callers to ext2fs_block_iterate so that some
private data structure can be passed to the callback function. The
blockcnt parameter, if non-negative, indicates the logical block
number of a data block in the inode. If blockcnt is less than
zero, then func was called on a metadata block, and blockcnt
will be one of the following values: BLOCK_COUNT_IND, BLOCK_COUNT_DIND,
BLOCK_COUNT_TIND, or BLOCK_COUNT_TRANSLATOR. The blocknr is a
pointer to the inode or indirect block entry listing physical block
number. The callback function may modify the physical block number, if
it returns the BLOCK_CHANGED flag.
The callback function func returns a result code which is composed of
the logical OR of the following flags:
`BLOCK_CHANGED'
This flag indicates that callback function has modified the physical
block number pointed to by blocknr.
`BLOCK_ABORT'
This flag requests that ext2fs_block_iterate to stop immediately
and return to the caller.
Function: errcode_t ext2fs_block_iterate2(ext2_filsys fs, ext2_ino_t ino, int flags, char *block_buf, int (*func)(ext2_filsys fs, blk_t *blocknr, e2_blkcnt_t blockcnt, blk_t ref_blk, int ref_offset, void *private), void *private)
This function is much like ext2fs_block_iterate2, except that the
blockcnt type is a 64-bit signed quantity, to support larger
files, and the addition of the ref_blk and ref_offset
arguments passed to the callback function, which identify the location
of the physical block pointed to by pointer blocknr. If
ref_blk is zero, then ref_offset contains the offset into
the i_blocks array. If ref_blk is non-zero, then the physical
block location is contained inside an indirect block group, and
ref_offset contains the offset into the indirect block.
Returns 0 if ino is a directory, and ENOTDIR if it is not.
Function: int ext2_inode_has_valid_blocks(struct ext2_inode *inode)
Returns 1 if the inode's block entries actually valid block entries, and
0 if not. Inodes which represent devices and fast symbolic links do not
contain valid block entries.
This function creates a new directory block in block. If
dir_ino is non-zero, then dir_info and parent_ino is used
to initialize directory entries for `.' and `..', respectively.
Function: errcode_t ext2fs_dir_iterate(ext2_filsys fs, ext2_ino_t dir, int flags, char *block_buf, int (*func)(struct ext2_dir_entry *dirent, int offset, int blocksize, char *buf, void *private), void *private)
This function interates over all of the directory entries in the
directory dir, calling the callback function func for each
directory entry in the directory. The block_buf parameter should
either be NULL, or if the ext2fs_dir_iterate function is
called repeatedly, the overhead of allocating and freeing
scratch memory can be avoided by passing a pointer to a scratch buffer
which must be at least as big as the filesystem's blocksize.
The flags parameter controls how the iterator will function:
`DIRENT_FLAG_INCLUDE_EMPTY'
This flag indicates that the callback function should be called even
for deleted or empty directory entries.
This function creates a new directory. If inum is zero, then a
new inode will be allocated; otherwise, the directory will be created in
the inode specified by inum. If name specifies the name of
the new directory; if it is non-NULL, then the new directory will be
linked into the parent directory parent.
This function adds a new empty directory block and appends it to
the directory dir. This allows functions such as
ext2fs_link to add new directory entries to a directory which is full.
This function adds a new directory entry to the directory dir,
with name and ino specifying the name and inode number in
the directory entry, respectively.
The low 3 bits of the flags field is used to specify the file type of
inode: (No other flags are currently defined.)
This function removes a directory entry from dir.
The directory entry to be removed is the first one which is
matched by name and ino. If name is non-NULL,
the directory entry's name must match name. If ino is
non-zero, the directory entry's inode number must match ino.
No flags are currently defined for ext2fs_unlink; callers should
pass in zero to this parameter.
Function: int ext2fs_fast_test_inode_bitmap(ext2fs_inode_bitmap bitmap, ext2_ino_t inode)
These "fast" functions are like their normal counterparts; however,
they are implemented as inline functions and do not perform bounds
checks on the inode number or block number; they are assumed to be
correct. They should only be used in speed-critical applications, where
the inode or block number has already been validated by other means.
The dblist abstraction stores a list of blocks belonging to
directories. This list can be useful when a program needs to interate
over all directory entries in a filesystem; e2fsck does this in
pass 2 of its operations, and debugfs needs to do this when it is
trying to turn an inode number into a pathname.
This iterator calls func for every entry in the dblist data structure.
Function: errcode_t ext2fs_dblist_dir_iterate(ext2_dblist dblist, int flags, char *block_buf, int (*func)(ext2_ino_t dir, int entry, struct ext2_dir_entry *dirent, int offset, int blocksize, char *buf, void *private), void *private)
This iterator takes reads in the directory block indicated in each
dblist entry, and calls func for each directory entry in each
directory block. If dblist contains all the directory blocks in a
filesystem, this function provides a convenient way to iterate over all
directory entries for that filesystem.
The icount abstraction is a specialized data type used by e2fsck
to store how many times a particular inode is referenced by the
filesystem. This is used twice; once to store the actual number of times
that the inode is reference; and once to store the claimed number of times
the inode is referenced according to the inode structure.
This abstraction is designed to be extremely efficient for storing this
sort of information, by taking advantage of the following properties of
inode counts, namely (1) inode counts are very often zero (because
the inode is currrently not in use), and (2) many files have a inode
count of 1 (because they are a file which has no additional hard links).
Function: errcode_t ext2fs_create_icount2(ext2_filsys fs, int flags, int size, ext2_icount_t hint, ext2_icount_t *ret)
Creates an icount stucture for a filesystem fs, with initial space
for size inodes whose count is greater than 1. The flags
parameter is either 0 or EXT2_ICOUNT_OPT_INCREMENT, which
indicates that icount structure should be able to increment inode counts
quickly. The icount structure is returned in ret. The returned
icount structure initially has a count of zero for all inodes.
The hint parameter allows the caller to optionally pass in another
icount structure which is used to initialize the array of inodes whose
count is greater than 1. It is used purely as a speed optimization so
that the icount structure can determine in advance which inodes are
likely to contain a count grater than 1.
Validates the internal rep invariant of icount; if there are any
problems, print out debugging information to f. This function is
intended for debugging and testing use only.
Function: errcode_t ext2fs_get_device_size(const char *file, int blocksize, blk_t *retblocks)
/* ismounted.c */
Function: errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
/* version.c */
Function: int ext2fs_get_library_version(const char **ver_string, const char **date_string)
This function returns the current version of the ext2 library. The
return value contains an integer version code, which consists of the
major version number of the library multiplied by 100, plus the minor
version number of the library. Hence, if the library version is 1.08,
the returned value will be 108.
If ver_string and/or date_string are non-NULL, they will be
set to point at a constant string containing the library version and/or
release date, respectively.
Function: int ext2fs_parse_version_string(const char *ver_string)
This function takes a version string which may included in an
application and returns a version code using the same algorithm used by
ext2fs_get_library_version. It can be used by programs included
in the e2fsprogs distribution to assure that they are using an
up-to-date ext2 shared library.
/* inline functions */
Function: int ext2fs_group_of_blk(ext2_filsys fs, blk_t blk)
This function returns the block group which contains the block blk.
Function: int ext2fs_group_of_ino(ext2_filsys fs, ext2_ino_t ino)
This function returns the block group which contains the inode ino.