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Kernel: Fix storage device read/write for request length < block size

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The current implementation of read/write will fail in StorageDevice
when the request length is less than the block size of the underlying
device. Fix it by calculating the offset within a block for such cases
and using it for copying data from the bounce buffer.
This commit is contained in:
Pankaj Raghav 2022-03-28 21:01:46 +02:00 • committed by Idan Horowitz
parent 34db0dab41
commit 36363b1a37
1 changed files with 10 additions and 2 deletions
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12
Kernel/Storage/StorageDevice.cpp
View file

@ -30,6 +30,7 @@ StringView StorageDevice::class_name() const
ErrorOr<size_t> StorageDevice::read(OpenFileDescription&, u64 offset, UserOrKernelBuffer& outbuf, size_t len)
{
u64 index = offset >> block_size_log();
off_t offset_within_block = 0;
size_t whole_blocks = len >> block_size_log();
size_t remaining = len - (whole_blocks << block_size_log());
@ -40,6 +41,9 @@ ErrorOr<size_t> StorageDevice::read(OpenFileDescription&, u64 offset, UserOrKern
remaining = 0;
}
if (len < block_size())
offset_within_block = offset - (index << block_size_log());
dbgln_if(STORAGE_DEVICE_DEBUG, "StorageDevice::read() index={}, whole_blocks={}, remaining={}", index, whole_blocks, remaining);
if (whole_blocks > 0) {
@ -78,7 +82,7 @@ ErrorOr<size_t> StorageDevice::read(OpenFileDescription&, u64 offset, UserOrKern
default:
break;
}
TRY(outbuf.write(data.data(), pos, remaining));
TRY(outbuf.write(data.offset_pointer(offset_within_block), pos, remaining));
}
return pos + remaining;
@ -92,6 +96,7 @@ bool StorageDevice::can_read(const OpenFileDescription&, u64 offset) const
ErrorOr<size_t> StorageDevice::write(OpenFileDescription&, u64 offset, const UserOrKernelBuffer& inbuf, size_t len)
{
u64 index = offset >> block_size_log();
off_t offset_within_block = 0;
size_t whole_blocks = len >> block_size_log();
size_t remaining = len - (whole_blocks << block_size_log());
@ -102,6 +107,9 @@ ErrorOr<size_t> StorageDevice::write(OpenFileDescription&, u64 offset, const Use
remaining = 0;
}
if (len < block_size())
offset_within_block = offset - (index << block_size_log());
// We try to allocate the temporary block buffer for partial writes *before* we start any full block writes,
// to try and prevent partial writes
Optional<ByteBuffer> partial_write_block;
@ -151,7 +159,7 @@ ErrorOr<size_t> StorageDevice::write(OpenFileDescription&, u64 offset, const Use
}
}
TRY(inbuf.read(partial_write_block->data(), pos, remaining));
TRY(inbuf.read(partial_write_block->offset_pointer(offset_within_block), pos, remaining));
{
auto write_request = TRY(try_make_request<AsyncBlockDeviceRequest>(AsyncBlockDeviceRequest::Write, index + whole_blocks, 1, data_buffer, block_size()));