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download PDF document: vn_deallocate.9.pdf

VN_DEALLOCATE(9) FreeBSD Kernel Developer's Manual VN_DEALLOCATE(9)
NAME vn_deallocate - zero and/or deallocate storage from a file
SYNOPSIS #include <sys/param.h> #include <sys/vnode.h>
int vn_deallocate(struct vnode *vp, off_t *offset, off_t *length, int flags, int ioflag, struct ucred *active_cred, struct ucred *file_cred);
DESCRIPTION The vn_deallocate() function zeros and/or deallocates backing storage space from a file. This function only works on vnodes with VREG type.
The arguments are:
vp The vnode of the file.
offset The starting offset of the operation range.
length The length of the operation range. This must be greater than 0.
flags The control flags of the operation. This should be set to 0 for now.
ioflag Directives and hints to be given to the file system.
active_cred The user credentials of the calling thread.
file_cred The credentials installed on the file description pointing to the vnode or NOCRED.
The ioflag() argument gives directives and hints to the file system. It may include one or more of the following flags:
IO_NODELOCKED The vnode was locked before the call.
IO_RANGELOCKED Rangelock was owned around the call.
IO_NOMACCHECK Skip MAC checking in the call.
IO_SYNC Do I/O synchronously.
IO_DIRECT Attempt to bypass buffer cache.
*offset and *length are updated to reflect the unprocessed operation range of the call. For a successful completion, *length is updated to be the value 0, and *offset is incremented by the number of bytes zeroed before the end-of-file.
RETURN VALUES Upon successful completion, the value 0 is returned; otherwise the appropriate error is returned.
SEE ALSO