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71be6b4942
Add a new fallocate mode flag that explicitly unshares blocks on filesystems that support such features. The new flag can only be used with an allocate-mode fallocate call. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
80 lines
3.5 KiB
C
80 lines
3.5 KiB
C
#ifndef _UAPI_FALLOC_H_
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#define _UAPI_FALLOC_H_
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#define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */
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#define FALLOC_FL_PUNCH_HOLE 0x02 /* de-allocates range */
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#define FALLOC_FL_NO_HIDE_STALE 0x04 /* reserved codepoint */
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/*
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* FALLOC_FL_COLLAPSE_RANGE is used to remove a range of a file
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* without leaving a hole in the file. The contents of the file beyond
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* the range being removed is appended to the start offset of the range
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* being removed (i.e. the hole that was punched is "collapsed"),
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* resulting in a file layout that looks like the range that was
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* removed never existed. As such collapsing a range of a file changes
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* the size of the file, reducing it by the same length of the range
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* that has been removed by the operation.
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*
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* Different filesystems may implement different limitations on the
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* granularity of the operation. Most will limit operations to
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* filesystem block size boundaries, but this boundary may be larger or
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* smaller depending on the filesystem and/or the configuration of the
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* filesystem or file.
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*
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* Attempting to collapse a range that crosses the end of the file is
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* considered an illegal operation - just use ftruncate(2) if you need
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* to collapse a range that crosses EOF.
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*/
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#define FALLOC_FL_COLLAPSE_RANGE 0x08
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/*
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* FALLOC_FL_ZERO_RANGE is used to convert a range of file to zeros preferably
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* without issuing data IO. Blocks should be preallocated for the regions that
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* span holes in the file, and the entire range is preferable converted to
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* unwritten extents - even though file system may choose to zero out the
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* extent or do whatever which will result in reading zeros from the range
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* while the range remains allocated for the file.
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*
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* This can be also used to preallocate blocks past EOF in the same way as
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* with fallocate. Flag FALLOC_FL_KEEP_SIZE should cause the inode
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* size to remain the same.
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*/
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#define FALLOC_FL_ZERO_RANGE 0x10
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/*
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* FALLOC_FL_INSERT_RANGE is use to insert space within the file size without
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* overwriting any existing data. The contents of the file beyond offset are
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* shifted towards right by len bytes to create a hole. As such, this
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* operation will increase the size of the file by len bytes.
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*
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* Different filesystems may implement different limitations on the granularity
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* of the operation. Most will limit operations to filesystem block size
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* boundaries, but this boundary may be larger or smaller depending on
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* the filesystem and/or the configuration of the filesystem or file.
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*
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* Attempting to insert space using this flag at OR beyond the end of
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* the file is considered an illegal operation - just use ftruncate(2) or
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* fallocate(2) with mode 0 for such type of operations.
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*/
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#define FALLOC_FL_INSERT_RANGE 0x20
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/*
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* FALLOC_FL_UNSHARE_RANGE is used to unshare shared blocks within the
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* file size without overwriting any existing data. The purpose of this
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* call is to preemptively reallocate any blocks that are subject to
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* copy-on-write.
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*
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* Different filesystems may implement different limitations on the
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* granularity of the operation. Most will limit operations to filesystem
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* block size boundaries, but this boundary may be larger or smaller
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* depending on the filesystem and/or the configuration of the filesystem
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* or file.
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*
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* This flag can only be used with allocate-mode fallocate, which is
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* to say that it cannot be used with the punch, zero, collapse, or
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* insert range modes.
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*/
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#define FALLOC_FL_UNSHARE_RANGE 0x40
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#endif /* _UAPI_FALLOC_H_ */
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