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Commit 6f6210dd authored by Daichi Hirono's avatar Daichi Hirono
Browse files

Retry write operation when getting ENOBUFS. 

Previously libappfuse set SO_SNDBUF to the maximum message size. However
it does not prevent ENOBUF and it made AppFusePerfTest#testReadWriteFile
flaky.

The CL let FuseBuffer retry write operation when getting ENOBUFS.

Bug: 34903085
Test: libappfuse
Change-Id: I1602474d852e1599f6e69103bcf6f18277a5644b
parent 281531bd

libappfuse/FuseBuffer.cc

+30 −21
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ namespace android { 
namespace fuse {

namespace {



constexpr useconds_t kRetrySleepForWriting = 1000;  // 1 ms



template <typename T>

bool CheckHeaderLength(const FuseMessage<T>* self, const char* name, size_t max_size) {

    const auto& header = static_cast<const T*>(self)->header;
@@ -91,6 +93,7 @@ ResultOrAgain WriteInternal(const FuseMessage<T>* self, int fd, int sockflag, co 
    const char* const buf = reinterpret_cast<const char*>(self);

    const auto& header = static_cast<const T*>(self)->header;



    while (true) {

        int result;

        if (sockflag) {

            CHECK(data == nullptr);
@@ -102,19 +105,25 @@ ResultOrAgain WriteInternal(const FuseMessage<T>* self, int fd, int sockflag, co 
        } else {

            result = TEMP_FAILURE_RETRY(write(fd, buf, header.len));

        }



        if (result == -1) {

        if (errno == EAGAIN) {

            switch (errno) {

                case ENOBUFS:

                    // When returning ENOBUFS, epoll still reports the FD is writable. Just usleep

                    // and retry again.

                    usleep(kRetrySleepForWriting);

                    continue;

                case EAGAIN:

                    return ResultOrAgain::kAgain;

        }

                default:

                    PLOG(ERROR) << "Failed to write a FUSE message";

                    return ResultOrAgain::kFailure;

            }



        }

        CHECK(static_cast<uint32_t>(result) == header.len);

        return ResultOrAgain::kSuccess;

    }

}

}



static_assert(std::is_standard_layout<FuseBuffer>::value,

              "FuseBuffer must be standard layout union.");
@@ -161,7 +170,7 @@ bool FuseMessage<T>::Write(int fd) const { 
template <typename T>

bool FuseMessage<T>::WriteWithBody(int fd, size_t max_size, const void* data) const {

    CHECK(data != nullptr);

    return WriteInternal<T>(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;

    return WriteInternal(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;

}



template <typename T>