Viewing: llapi_get_lum_file_fd.3
.TH LLAPI_GET_LUM_FILE_FD 3 2024-08-27 "Lustre User API" "Lustre Library Functions"
.SH NAME
llapi_get_lum_file_fd, llapi_get_lum_dir_fd, llapi_get_lum_file, llapi_get_lum_dir \- get valid file attributes and LOV stripe information to the user.
.SH SYNOPSIS
.nf
.B #include <lustre/lustreapi.h>
.PP
.BI "int llapi_get_lum_file_fd(int " dir_fd ", const char *" fname ",
.BI " __u64 *" valid ", lstatx_t *" statx ",
.BI " struct lov_user_md *" lum ",
.BI " size_t " lumsize ");"
.PP
.BI "int llapi_get_lum_dir_fd(int " dir_fd ", __u64 *" valid ",
.BI " lstatx_t *" statx ", struct lov_user_md *" lum ",
.BI " size_t " lumsize ");"
.PP
.BI "int llapi_get_lum_file(const char *" path ", __u64 *" valid ",
.BI " lstatx_t *" statx ", struct lov_user_md *" lum ",
.BI " size_t " lumsize ");"
.PP
.BI "int llapi_get_lum_dir(const char *" path ", __u64 *" valid ",
.BI " lstatx_t *" statx ", struct lov_user_md *" lum ",
.BI " size_t " lumsize ");"
.fi
.SH DESCRIPTION
The function
.BR llapi_get_lum_file_fd() ,
.BR llapi_get_lum_dir_fd() ,
.BR llapi_get_lum_file() ,
and
.BR llapi_get_lum_dir()
returns file attributes and LOV stripe information by an ioctl on the dir.
.BR dir_fd
is a file descriptor that refers to a directory. For function
.BR llapi_get_lum_file_fd() ,
if
.BR fname
is provided, it is a relative pathname that is interpreted relative to the
directory referred to by
.BR dir_fd .
.P
The function
.BR llapi_get_lum_dir_fd() ,
.BR llapi_get_lum_file() ,
and
.BR llapi_get_lum_dir()
can be used for applications that are only processing a single file or directory
referred to by
.BR dir_fd
or
.BR path .
.P
The function
.BR llapi_get_lum_file_fd()
can be used for applications that process lots of files. It avoids opening,
locking, and closing each file on the client if that is not needed. Multiple
calls of this llapi can be done on the parent dir referenced by
.B dir_fd
with a single open for all files in that directory, and it also does not
pollute the client dcache with millions of dentries when traversing a large
filesystem.
.P
The stripe information for the target file is returned to the user in the
.B struct lov_user_md
pointed to by
.BR lum
if it is not a NULL pointer. The file attribute information for the target file
is returned in the
.BR lstatx_t
structure pointed to by
.BR statx
if it is not a NULL pointer.
The output argument
.BR valid
contains the flags to indicate which fields in the returned file attributes
have been validly filled in.
.P
The valid flags are as follows:
.TP 20
OBD_MD_FLSIZE
The returned file size is known strictly correct.
.TP
OBD_MD_FLBLOCKS
The returned file blocks is known strictly correct.
.TP
OBD_MD_FLLAZYSIZE
The returned file size is approximate, may never have been strictly correct.
.TP
OBD_MD_FLLAZYBLOCKS
The returned file blocks is approximate, may never have been strictly correct.
.TP
OBD_MD_FLID
The returned object ID is valid.
.TP
OBD_MD_FLATIME
The returned access time is valid.
.TP
OBD_MD_FLMTIME
The returned data modification time is valid.
.TP
OBD_MD_FLCTIME
The returned change time is valid.
.TP
OBD_MD_FLBLKSZ
The returned block size is valid.
.TP
OBD_MD_FLMODE
The returned access bits (mode & ~S_IFMT) is valid.
.TP
OBD_MD_FLTYPE
The returned object type (mode & S_IFMT) is valid.
.TP
OBD_MD_FLUID
The returned user ID is valid.
.TP
OBD_MD_FLGID
The returned group ID is valid.
.TP
OBD_MD_FLFLAGS
The returned flags word is valid.
.TP
OBD_MD_FLNLINK
The returned link count is valid.
.TP
OBD_MD_FLRDEV
The returned device number is valid.
.SH RETURN VALUES
.LP
.BR llapi_get_lum_file_fd() ,
.BR llapi_get_lum_dir_fd() ,
.BR llapi_get_lum_file() ,
and
.BR llapi_get_lum_dir()
return 0 on success or a negative errno value on failure.
.SH ERRORS
.TP 15
.B -ENOMEM
Insufficient memory to complete operation.
.TP
.B -EFAULT
Memory region is not properly mapped.
.TP
.B -EINVAL
One or more invalid arguments are given.
.TP
.B -EOPNOTSUPP
The operation is not supported.
.TP
.B -ENOTTY
File does not reside on a Lustre filesystem.
.TP
.B -ENOENT
.I path
does not exist.
.TP
.B -EBADF
.I dir_fd
is not a valid open file descriptor.
.SH AVAILABILITY
.BR llapi_get_lum_file_fd() ,
.BR llapi_get_lum_file() ,
.B llapi_get_lum_dir_fd()
and
.B llapi_get_lum_dir()
are part of the
.BR lustre (7)
user application interface library since release 2.13.0
.\" Added in commit v2_12_58-78-g11aa7f8704
.SH SEE ALSO
.BR lustreapi (7)
