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qemu/tools/virtiofsd/fuse_common.h

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/*
* FUSE: Filesystem in Userspace
* Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
*
* This program can be distributed under the terms of the GNU LGPLv2.
* See the file COPYING.LIB.
*/
/** @file */
#if !defined(FUSE_H_) && !defined(FUSE_LOWLEVEL_H_)
#error \
"Never include <fuse_common.h> directly; use <fuse.h> or <fuse_lowlevel.h> instead."
#endif
#ifndef FUSE_COMMON_H_
#define FUSE_COMMON_H_
#include "fuse_log.h"
#include "fuse_opt.h"
/** Major version of FUSE library interface */
#define FUSE_MAJOR_VERSION 3
/** Minor version of FUSE library interface */
#define FUSE_MINOR_VERSION 2
#define FUSE_MAKE_VERSION(maj, min) ((maj) * 10 + (min))
#define FUSE_VERSION FUSE_MAKE_VERSION(FUSE_MAJOR_VERSION, FUSE_MINOR_VERSION)
/**
* Information about an open file.
*
* File Handles are created by the open, opendir, and create methods and closed
* by the release and releasedir methods. Multiple file handles may be
* concurrently open for the same file. Generally, a client will create one
* file handle per file descriptor, though in some cases multiple file
* descriptors can share a single file handle.
*/
struct fuse_file_info {
/** Open flags. Available in open() and release() */
int flags;
/*
* In case of a write operation indicates if this was caused
* by a delayed write from the page cache. If so, then the
* context's pid, uid, and gid fields will not be valid, and
* the *fh* value may not match the *fh* value that would
* have been sent with the corresponding individual write
* requests if write caching had been disabled.
*/
unsigned int writepage:1;
/** Can be filled in by open, to use direct I/O on this file. */
unsigned int direct_io:1;
/*
* Can be filled in by open. It signals the kernel that any
* currently cached file data (ie., data that the filesystem
* provided the last time the file was open) need not be
* invalidated. Has no effect when set in other contexts (in
* particular it does nothing when set by opendir()).
*/
unsigned int keep_cache:1;
/*
* Indicates a flush operation. Set in flush operation, also
* maybe set in highlevel lock operation and lowlevel release
* operation.
*/
unsigned int flush:1;
/*
* Can be filled in by open, to indicate that the file is not
* seekable.
*/
unsigned int nonseekable:1;
/*
* Indicates that flock locks for this file should be
* released. If set, lock_owner shall contain a valid value.
* May only be set in ->release().
*/
unsigned int flock_release:1;
/*
* Can be filled in by opendir. It signals the kernel to
* enable caching of entries returned by readdir(). Has no
* effect when set in other contexts (in particular it does
* nothing when set by open()).
*/
unsigned int cache_readdir:1;
/* Indicates that suid/sgid bits should be removed upon write */
unsigned int kill_priv:1;
/** Padding. Reserved for future use*/
unsigned int padding:24;
unsigned int padding2:32;
/*
* File handle id. May be filled in by filesystem in create,
* open, and opendir(). Available in most other file operations on the
* same file handle.
*/
uint64_t fh;
/** Lock owner id. Available in locking operations and flush */
uint64_t lock_owner;
/*
* Requested poll events. Available in ->poll. Only set on kernels
* which support it. If unsupported, this field is set to zero.
*/
uint32_t poll_events;
};
/*
* Capability bits for 'fuse_conn_info.capable' and 'fuse_conn_info.want'
*/
/**
* Indicates that the filesystem supports asynchronous read requests.
*
* If this capability is not requested/available, the kernel will
* ensure that there is at most one pending read request per
* file-handle at any time, and will attempt to order read requests by
* increasing offset.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_ASYNC_READ (1 << 0)
/**
* Indicates that the filesystem supports "remote" locking.
*
* This feature is enabled by default when supported by the kernel,
* and if getlk() and setlk() handlers are implemented.
*/
#define FUSE_CAP_POSIX_LOCKS (1 << 1)
/**
* Indicates that the filesystem supports the O_TRUNC open flag. If
* disabled, and an application specifies O_TRUNC, fuse first calls
* truncate() and then open() with O_TRUNC filtered out.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_ATOMIC_O_TRUNC (1 << 3)
/**
* Indicates that the filesystem supports lookups of "." and "..".
*
* This feature is disabled by default.
*/
#define FUSE_CAP_EXPORT_SUPPORT (1 << 4)
/**
* Indicates that the kernel should not apply the umask to the
* file mode on create operations.
*
* This feature is disabled by default.
*/
#define FUSE_CAP_DONT_MASK (1 << 6)
/**
* Indicates that libfuse should try to use splice() when writing to
* the fuse device. This may improve performance.
*
* This feature is disabled by default.
*/
#define FUSE_CAP_SPLICE_WRITE (1 << 7)
/**
* Indicates that libfuse should try to move pages instead of copying when
* writing to / reading from the fuse device. This may improve performance.
*
* This feature is disabled by default.
*/
#define FUSE_CAP_SPLICE_MOVE (1 << 8)
/**
* Indicates that libfuse should try to use splice() when reading from
* the fuse device. This may improve performance.
*
* This feature is enabled by default when supported by the kernel and
* if the filesystem implements a write_buf() handler.
*/
#define FUSE_CAP_SPLICE_READ (1 << 9)
/**
* If set, the calls to flock(2) will be emulated using POSIX locks and must
* then be handled by the filesystem's setlock() handler.
*
* If not set, flock(2) calls will be handled by the FUSE kernel module
* internally (so any access that does not go through the kernel cannot be taken
* into account).
*
* This feature is enabled by default when supported by the kernel and
* if the filesystem implements a flock() handler.
*/
#define FUSE_CAP_FLOCK_LOCKS (1 << 10)
/**
* Indicates that the filesystem supports ioctl's on directories.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_IOCTL_DIR (1 << 11)
/**
* Traditionally, while a file is open the FUSE kernel module only
* asks the filesystem for an update of the file's attributes when a
* client attempts to read beyond EOF. This is unsuitable for
* e.g. network filesystems, where the file contents may change
* without the kernel knowing about it.
*
* If this flag is set, FUSE will check the validity of the attributes
* on every read. If the attributes are no longer valid (i.e., if the
* *attr_timeout* passed to fuse_reply_attr() or set in `struct
* fuse_entry_param` has passed), it will first issue a `getattr`
* request. If the new mtime differs from the previous value, any
* cached file *contents* will be invalidated as well.
*
* This flag should always be set when available. If all file changes
* go through the kernel, *attr_timeout* should be set to a very large
* number to avoid unnecessary getattr() calls.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_AUTO_INVAL_DATA (1 << 12)
/**
* Indicates that the filesystem supports readdirplus.
*
* This feature is enabled by default when supported by the kernel and if the
* filesystem implements a readdirplus() handler.
*/
#define FUSE_CAP_READDIRPLUS (1 << 13)
/**
* Indicates that the filesystem supports adaptive readdirplus.
*
* If FUSE_CAP_READDIRPLUS is not set, this flag has no effect.
*
* If FUSE_CAP_READDIRPLUS is set and this flag is not set, the kernel
* will always issue readdirplus() requests to retrieve directory
* contents.
*
* If FUSE_CAP_READDIRPLUS is set and this flag is set, the kernel
* will issue both readdir() and readdirplus() requests, depending on
* how much information is expected to be required.
*
* As of Linux 4.20, the algorithm is as follows: when userspace
* starts to read directory entries, issue a READDIRPLUS request to
* the filesystem. If any entry attributes have been looked up by the
* time userspace requests the next batch of entries continue with
* READDIRPLUS, otherwise switch to plain READDIR. This will reasult
* in eg plain "ls" triggering READDIRPLUS first then READDIR after
* that because it doesn't do lookups. "ls -l" should result in all
* READDIRPLUS, except if dentries are already cached.
*
* This feature is enabled by default when supported by the kernel and
* if the filesystem implements both a readdirplus() and a readdir()
* handler.
*/
#define FUSE_CAP_READDIRPLUS_AUTO (1 << 14)
/**
* Indicates that the filesystem supports asynchronous direct I/O submission.
*
* If this capability is not requested/available, the kernel will ensure that
* there is at most one pending read and one pending write request per direct
* I/O file-handle at any time.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_ASYNC_DIO (1 << 15)
/**
* Indicates that writeback caching should be enabled. This means that
* individual write request may be buffered and merged in the kernel
* before they are send to the filesystem.
*
* This feature is disabled by default.
*/
#define FUSE_CAP_WRITEBACK_CACHE (1 << 16)
/**
* Indicates support for zero-message opens. If this flag is set in
* the `capable` field of the `fuse_conn_info` structure, then the
* filesystem may return `ENOSYS` from the open() handler to indicate
* success. Further attempts to open files will be handled in the
* kernel. (If this flag is not set, returning ENOSYS will be treated
* as an error and signaled to the caller).
*
* Setting (or unsetting) this flag in the `want` field has *no
* effect*.
*/
#define FUSE_CAP_NO_OPEN_SUPPORT (1 << 17)
/**
* Indicates support for parallel directory operations. If this flag
* is unset, the FUSE kernel module will ensure that lookup() and
* readdir() requests are never issued concurrently for the same
* directory.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_PARALLEL_DIROPS (1 << 18)
/**
* Indicates support for POSIX ACLs.
*
* If this feature is enabled, the kernel will cache and have
* responsibility for enforcing ACLs. ACL will be stored as xattrs and
* passed to userspace, which is responsible for updating the ACLs in
* the filesystem, keeping the file mode in sync with the ACL, and
* ensuring inheritance of default ACLs when new filesystem nodes are
* created. Note that this requires that the file system is able to
* parse and interpret the xattr representation of ACLs.
*
* Enabling this feature implicitly turns on the
* ``default_permissions`` mount option (even if it was not passed to
* mount(2)).
*
* This feature is disabled by default.
*/
#define FUSE_CAP_POSIX_ACL (1 << 19)
/**
* Indicates that the filesystem is responsible for unsetting
* setuid and setgid bits when a file is written, truncated, or
* its owner is changed.
*
* This feature is enabled by default when supported by the kernel.
*/
#define FUSE_CAP_HANDLE_KILLPRIV (1 << 20)
/**
* Indicates support for zero-message opendirs. If this flag is set in
* the `capable` field of the `fuse_conn_info` structure, then the filesystem
* may return `ENOSYS` from the opendir() handler to indicate success. Further
* opendir and releasedir messages will be handled in the kernel. (If this
* flag is not set, returning ENOSYS will be treated as an error and signalled
* to the caller.)
*
* Setting (or unsetting) this flag in the `want` field has *no effect*.
*/
#define FUSE_CAP_NO_OPENDIR_SUPPORT (1 << 24)
/**
* Indicates that the kernel supports the FUSE_ATTR_SUBMOUNT flag.
*
* Setting (or unsetting) this flag in the `want` field has *no effect*.
*/
#define FUSE_CAP_SUBMOUNTS (1 << 27)
/**
* Indicates that the filesystem is responsible for clearing
* security.capability xattr and clearing setuid and setgid bits. Following
* are the rules.
* - clear "security.capability" on write, truncate and chown unconditionally
* - clear suid/sgid if following is true. Note, sgid is cleared only if
* group executable bit is set.
* o setattr has FATTR_SIZE and FATTR_KILL_SUIDGID set.
* o setattr has FATTR_UID or FATTR_GID
* o open has O_TRUNC and FUSE_OPEN_KILL_SUIDGID
* o create has O_TRUNC and FUSE_OPEN_KILL_SUIDGID flag set.
* o write has FUSE_WRITE_KILL_SUIDGID
*/
#define FUSE_CAP_HANDLE_KILLPRIV_V2 (1 << 28)
/**
* Ioctl flags
*
* FUSE_IOCTL_COMPAT: 32bit compat ioctl on 64bit machine
* FUSE_IOCTL_UNRESTRICTED: not restricted to well-formed ioctls, retry allowed
* FUSE_IOCTL_RETRY: retry with new iovecs
* FUSE_IOCTL_DIR: is a directory
*
* FUSE_IOCTL_MAX_IOV: maximum of in_iovecs + out_iovecs
*/
#define FUSE_IOCTL_COMPAT (1 << 0)
#define FUSE_IOCTL_UNRESTRICTED (1 << 1)
#define FUSE_IOCTL_RETRY (1 << 2)
#define FUSE_IOCTL_DIR (1 << 4)
#define FUSE_IOCTL_MAX_IOV 256
/**
* Connection information, passed to the ->init() method
*
* Some of the elements are read-write, these can be changed to
* indicate the value requested by the filesystem. The requested
* value must usually be smaller than the indicated value.
*/
struct fuse_conn_info {
/**
* Major version of the protocol (read-only)
*/
unsigned proto_major;
/**
* Minor version of the protocol (read-only)
*/
unsigned proto_minor;
/**
* Maximum size of the write buffer
*/
unsigned max_write;
/**
* Maximum size of read requests. A value of zero indicates no
* limit. However, even if the filesystem does not specify a
* limit, the maximum size of read requests will still be
* limited by the kernel.
*
* NOTE: For the time being, the maximum size of read requests
* must be set both here *and* passed to fuse_session_new()
* using the ``-o max_read=<n>`` mount option. At some point
* in the future, specifying the mount option will no longer
* be necessary.
*/
unsigned max_read;
/**
* Maximum readahead
*/
unsigned max_readahead;
/**
* Capability flags that the kernel supports (read-only)
*/
unsigned capable;
/**
* Capability flags that the filesystem wants to enable.
*
* libfuse attempts to initialize this field with
* reasonable default values before calling the init() handler.
*/
unsigned want;
/**
* Maximum number of pending "background" requests. A
* background request is any type of request for which the
* total number is not limited by other means. As of kernel
* 4.8, only two types of requests fall into this category:
*
* 1. Read-ahead requests
* 2. Asynchronous direct I/O requests
*
* Read-ahead requests are generated (if max_readahead is
* non-zero) by the kernel to preemptively fill its caches
* when it anticipates that userspace will soon read more
* data.
*
* Asynchronous direct I/O requests are generated if
* FUSE_CAP_ASYNC_DIO is enabled and userspace submits a large
* direct I/O request. In this case the kernel will internally
* split it up into multiple smaller requests and submit them
* to the filesystem concurrently.
*
* Note that the following requests are *not* background
* requests: writeback requests (limited by the kernel's
* flusher algorithm), regular (i.e., synchronous and
* buffered) userspace read/write requests (limited to one per
* thread), asynchronous read requests (Linux's io_submit(2)
* call actually blocks, so these are also limited to one per
* thread).
*/
unsigned max_background;
/**
* Kernel congestion threshold parameter. If the number of pending
* background requests exceeds this number, the FUSE kernel module will
* mark the filesystem as "congested". This instructs the kernel to
* expect that queued requests will take some time to complete, and to
* adjust its algorithms accordingly (e.g. by putting a waiting thread
* to sleep instead of using a busy-loop).
*/
unsigned congestion_threshold;
/**
* When FUSE_CAP_WRITEBACK_CACHE is enabled, the kernel is responsible
* for updating mtime and ctime when write requests are received. The
* updated values are passed to the filesystem with setattr() requests.
* However, if the filesystem does not support the full resolution of
* the kernel timestamps (nanoseconds), the mtime and ctime values used
* by kernel and filesystem will differ (and result in an apparent
* change of times after a cache flush).
*
* To prevent this problem, this variable can be used to inform the
* kernel about the timestamp granularity supported by the file-system.
* The value should be power of 10. The default is 1, i.e. full
* nano-second resolution. Filesystems supporting only second resolution
* should set this to 1000000000.
*/
unsigned time_gran;
/**
* For future use.
*/
unsigned reserved[22];
};
struct fuse_session;
struct fuse_pollhandle;
struct fuse_conn_info_opts;
/**
* This function parses several command-line options that can be used
* to override elements of struct fuse_conn_info. The pointer returned
* by this function should be passed to the
* fuse_apply_conn_info_opts() method by the file system's init()
* handler.
*
* Before using this function, think twice if you really want these
* parameters to be adjustable from the command line. In most cases,
* they should be determined by the file system internally.
*
* The following options are recognized:
*
* -o max_write=N sets conn->max_write
* -o max_readahead=N sets conn->max_readahead
* -o max_background=N sets conn->max_background
* -o congestion_threshold=N sets conn->congestion_threshold
* -o async_read sets FUSE_CAP_ASYNC_READ in conn->want
* -o sync_read unsets FUSE_CAP_ASYNC_READ in conn->want
* -o atomic_o_trunc sets FUSE_CAP_ATOMIC_O_TRUNC in conn->want
* -o no_remote_lock Equivalent to -o
*no_remote_flock,no_remote_posix_lock -o no_remote_flock Unsets
*FUSE_CAP_FLOCK_LOCKS in conn->want -o no_remote_posix_lock Unsets
*FUSE_CAP_POSIX_LOCKS in conn->want -o [no_]splice_write (un-)sets
*FUSE_CAP_SPLICE_WRITE in conn->want -o [no_]splice_move (un-)sets
*FUSE_CAP_SPLICE_MOVE in conn->want -o [no_]splice_read (un-)sets
*FUSE_CAP_SPLICE_READ in conn->want -o [no_]auto_inval_data (un-)sets
*FUSE_CAP_AUTO_INVAL_DATA in conn->want -o readdirplus=no unsets
*FUSE_CAP_READDIRPLUS in conn->want -o readdirplus=yes sets
*FUSE_CAP_READDIRPLUS and unsets FUSE_CAP_READDIRPLUS_AUTO in conn->want -o
*readdirplus=auto sets FUSE_CAP_READDIRPLUS and FUSE_CAP_READDIRPLUS_AUTO
*in conn->want -o [no_]async_dio (un-)sets FUSE_CAP_ASYNC_DIO in
*conn->want -o [no_]writeback_cache (un-)sets FUSE_CAP_WRITEBACK_CACHE in
*conn->want -o time_gran=N sets conn->time_gran
*
* Known options will be removed from *args*, unknown options will be
* passed through unchanged.
*
* @param args argument vector (input+output)
* @return parsed options
**/
struct fuse_conn_info_opts *fuse_parse_conn_info_opts(struct fuse_args *args);
/**
* This function applies the (parsed) parameters in *opts* to the
* *conn* pointer. It may modify the following fields: wants,
* max_write, max_readahead, congestion_threshold, max_background,
* time_gran. A field is only set (or unset) if the corresponding
* option has been explicitly set.
*/
void fuse_apply_conn_info_opts(struct fuse_conn_info_opts *opts,
struct fuse_conn_info *conn);
/**
* Go into the background
*
* @param foreground if true, stay in the foreground
* @return 0 on success, -1 on failure
*/
int fuse_daemonize(int foreground);
/**
* Get the version of the library
*
* @return the version
*/
int fuse_version(void);
/**
* Get the full package version string of the library
*
* @return the package version
*/
const char *fuse_pkgversion(void);
/**
* Destroy poll handle
*
* @param ph the poll handle
*/
void fuse_pollhandle_destroy(struct fuse_pollhandle *ph);
/*
* Data buffer
*/
/**
* Buffer flags
*/
enum fuse_buf_flags {
/**
* Buffer contains a file descriptor
*
* If this flag is set, the .fd field is valid, otherwise the
* .mem fields is valid.
*/
FUSE_BUF_IS_FD = (1 << 1),
/**
* Seek on the file descriptor
*
* If this flag is set then the .pos field is valid and is
* used to seek to the given offset before performing
* operation on file descriptor.
*/
FUSE_BUF_FD_SEEK = (1 << 2),
/**
* Retry operation on file descriptor
*
* If this flag is set then retry operation on file descriptor
* until .size bytes have been copied or an error or EOF is
* detected.
*/
FUSE_BUF_FD_RETRY = (1 << 3),
};
/**
* Single data buffer
*
* Generic data buffer for I/O, extended attributes, etc... Data may
* be supplied as a memory pointer or as a file descriptor
*/
struct fuse_buf {
/**
* Size of data in bytes
*/
size_t size;
/**
* Buffer flags
*/
enum fuse_buf_flags flags;
/**
* Memory pointer
*
* Used unless FUSE_BUF_IS_FD flag is set.
*/
void *mem;
/**
* File descriptor
*
* Used if FUSE_BUF_IS_FD flag is set.
*/
int fd;
/**
* File position
*
* Used if FUSE_BUF_FD_SEEK flag is set.
*/
off_t pos;
};
/**
* Data buffer vector
*
* An array of data buffers, each containing a memory pointer or a
* file descriptor.
*
* Allocate dynamically to add more than one buffer.
*/
struct fuse_bufvec {
/**
* Number of buffers in the array
*/
size_t count;
/**
* Index of current buffer within the array
*/
size_t idx;
/**
* Current offset within the current buffer
*/
size_t off;
/**
* Array of buffers
*/
struct fuse_buf buf[1];
};
/* Initialize bufvec with a single buffer of given size */
#define FUSE_BUFVEC_INIT(size__) \
((struct fuse_bufvec){ /* .count= */ 1, \
/* .idx = */ 0, \
/* .off = */ 0, /* .buf = */ \
{ /* [0] = */ { \
/* .size = */ (size__), \
/* .flags = */ (enum fuse_buf_flags)0, \
/* .mem = */ NULL, \
/* .fd = */ -1, \
/* .pos = */ 0, \
} } })
/**
* Get total size of data in a fuse buffer vector
*
* @param bufv buffer vector
* @return size of data
*/
size_t fuse_buf_size(const struct fuse_bufvec *bufv);
/**
* Copy data from one buffer vector to another
*
* @param dst destination buffer vector
* @param src source buffer vector
* @return actual number of bytes copied or -errno on error
*/
ssize_t fuse_buf_copy(struct fuse_bufvec *dst, struct fuse_bufvec *src);
/**
* Memory buffer iterator
*
*/
struct fuse_mbuf_iter {
/**
* Data pointer
*/
void *mem;
/**
* Total length, in bytes
*/
size_t size;
/**
* Offset from start of buffer
*/
size_t pos;
};
/* Initialize memory buffer iterator from a fuse_buf */
#define FUSE_MBUF_ITER_INIT(fbuf) \
((struct fuse_mbuf_iter){ \
.mem = fbuf->mem, \
.size = fbuf->size, \
.pos = 0, \
})
/**
* Consume bytes from a memory buffer iterator
*
* @param iter memory buffer iterator
* @param len number of bytes to consume
* @return pointer to start of consumed bytes or
* NULL if advancing beyond end of buffer
*/
void *fuse_mbuf_iter_advance(struct fuse_mbuf_iter *iter, size_t len);
/**
* Consume a NUL-terminated string from a memory buffer iterator
*
* @param iter memory buffer iterator
* @return pointer to the string or
* NULL if advancing beyond end of buffer or there is no NUL-terminator
*/
const char *fuse_mbuf_iter_advance_str(struct fuse_mbuf_iter *iter);
/*
* Signal handling
*/
/**
* Exit session on HUP, TERM and INT signals and ignore PIPE signal
*
* Stores session in a global variable. May only be called once per
* process until fuse_remove_signal_handlers() is called.
*
* Once either of the POSIX signals arrives, the signal handler calls
* fuse_session_exit().
*
* @param se the session to exit
* @return 0 on success, -1 on failure
*
* See also:
* fuse_remove_signal_handlers()
*/
int fuse_set_signal_handlers(struct fuse_session *se);
/**
* Restore default signal handlers
*
* Resets global session. After this fuse_set_signal_handlers() may
* be called again.
*
* @param se the same session as given in fuse_set_signal_handlers()
*
* See also:
* fuse_set_signal_handlers()
*/
void fuse_remove_signal_handlers(struct fuse_session *se);
/*
* Compatibility stuff
*/
#if !defined(FUSE_USE_VERSION) || FUSE_USE_VERSION < 30
#error only API version 30 or greater is supported
#endif
/*
* This interface uses 64 bit off_t.
*
* On 32bit systems please add -D_FILE_OFFSET_BITS=64 to your compile flags!
*/
QEMU_BUILD_BUG_ON(sizeof(off_t) != 8);
#endif /* FUSE_COMMON_H_ */
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