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Hole punch only if needed

This commit is contained in:
fedor 2024-08-04 21:53:40 -04:00
parent 029ee153cc
commit 8c569fc5f3
1 changed files with 14 additions and 10 deletions
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24
Sources/tart/OCI/Layerizer/DiskV2.swift
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@ -210,10 +210,19 @@ class DiskV2: Disk {
// If the local layer cache is used, only write chunks that differ
// since the base disk can contain anything at any position
if let rdisk = rdisk {
// F_PUNCHHOLE requires the holes to be aligned to file system block boundaries
let isHoleAligned = (offset % fsBlockSize) == 0 && (UInt64(chunk.count) % fsBlockSize) == 0
try rdisk.seek(toOffset: offset)
let actualContentsOnDisk = try rdisk.read(upToCount: chunk.count)
if isHoleAligned && chunk == zeroChunk {
if actualContentsOnDisk == chunk {
offset += UInt64(chunk.count)
continue
}
// F_PUNCHHOLE requires the holes to be aligned to file system block boundaries
let isAlignedForWholePunching = (offset % fsBlockSize) == 0 && (UInt64(chunk.count) % fsBlockSize) == 0
if chunk == zeroChunk {
var arg = fpunchhole_t(fp_flags: 0, reserved: 0, fp_offset: off_t(offset), fp_length: off_t(chunk.count))
if fcntl(disk.fileDescriptor, F_PUNCHHOLE, &arg) == -1 {
@ -222,13 +231,8 @@ class DiskV2: Disk {
throw RuntimeError.PullFailed("failed to punch hole: \(details)")
}
} else {
try rdisk.seek(toOffset: offset)
let actualContentsOnDisk = try rdisk.read(upToCount: chunk.count)
if chunk != actualContentsOnDisk {
try disk.seek(toOffset: offset)
disk.write(chunk)
}
try disk.seek(toOffset: offset)
disk.write(chunk)
}
offset += UInt64(chunk.count)