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vfs/block: correct transfer size allocation

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The calculations of packet_size and packet_count in the block_io() did
not consider rounding errors. This resulted in diverging values over
several bisecting operations (/= 2) and wrongly-size packet allocations
as well as memcpy operations.

Related to #2263 (comments about partial block accesses and
_block_io()).

Fixes #4471
This commit is contained in:
Christian Helmuth
2022-04-05 14:14:05 +02:00
parent dedcd0e294
commit fd9648f919
1 changed files with 6 additions and 9 deletions
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15
repos/os/src/lib/vfs/block_file_system.h
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@ -96,14 +96,12 @@ class Vfs::Block_file_system::Data_file_system : public Single_file_system
Block::Packet_descriptor::Opcode op; Block::Packet_descriptor::Opcode op;
op = write ? Block::Packet_descriptor::WRITE : Block::Packet_descriptor::READ; op = write ? Block::Packet_descriptor::WRITE : Block::Packet_descriptor::READ;
file_size packet_size = bulk ? sz : _block_size; size_t packet_count = bulk ? (size_t)(sz / _block_size) : 1;
file_size packet_count = bulk ? (sz / _block_size) : 1;
Block::Packet_descriptor packet; Block::Packet_descriptor packet;
/* sanity check */ /* sanity check */
if (packet_count > _block_buffer_count) { if (packet_count > _block_buffer_count) {
packet_size = _block_buffer_count * _block_size;
packet_count = _block_buffer_count; packet_count = _block_buffer_count;
} }
@ -111,7 +109,7 @@ class Vfs::Block_file_system::Data_file_system : public Single_file_system
try { try {
Mutex::Guard guard(_mutex); Mutex::Guard guard(_mutex);
packet = _block.alloc_packet((size_t)packet_size); packet = _block.alloc_packet(packet_count * _block_size);
break; break;
} catch (Block::Session::Tx::Source::Packet_alloc_failed) { } catch (Block::Session::Tx::Source::Packet_alloc_failed) {
@ -119,17 +117,16 @@ class Vfs::Block_file_system::Data_file_system : public Single_file_system
_ep.wait_and_dispatch_one_io_signal(); _ep.wait_and_dispatch_one_io_signal();
if (packet_count > 1) { if (packet_count > 1) {
packet_size /= 2;
packet_count /= 2; packet_count /= 2;
} }
} }
} }
Mutex::Guard guard(_mutex); Mutex::Guard guard(_mutex);
Block::Packet_descriptor p(packet, op, nr, (size_t)packet_count); Block::Packet_descriptor p(packet, op, nr, packet_count);
if (write) if (write)
Genode::memcpy(_tx_source->packet_content(p), buf, (size_t)packet_size); Genode::memcpy(_tx_source->packet_content(p), buf, packet_count * _block_size);
_tx_source->submit_packet(p); _tx_source->submit_packet(p);
@ -144,10 +141,10 @@ class Vfs::Block_file_system::Data_file_system : public Single_file_system
} }
if (!write) if (!write)
Genode::memcpy(buf, _tx_source->packet_content(p), (size_t)packet_size); Genode::memcpy(buf, _tx_source->packet_content(p), packet_count * _block_size);
_tx_source->release_packet(p); _tx_source->release_packet(p);
return packet_size; return packet_count * _block_size;
} }
public: public: