src/DiskIO/Mmapped/MmappedFile.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 47    Store Directory Routines
   5  */
   6
   7 #include "config.h"
   8 #include "DiskIO/IORequestor.h"
   9 #include "DiskIO/Mmapped/MmappedFile.h"
  10 #include "DiskIO/ReadRequest.h"
  11 #include "DiskIO/WriteRequest.h"
  12 #include <sys/mman.h>
  13
  14 CBDATA_CLASS_INIT(MmappedFile);
  15
  16 // helper class to deal with mmap(2) offset alignment and other low-level specs
  17 class Mmapping
  18 {
  19 public:
  20     Mmapping(int fd, size_t length, int prot, int flags, off_t offset);
  21     ~Mmapping();
  22
  23     void *map(); ///< calls mmap(2); returns usable buffer or nil on failure
  24     bool unmap(); ///< unmaps previously mapped buffer, if any
  25
  26 private:
  27     const int fd; ///< descriptor of the mmapped file
  28     const size_t length; ///< user-requested data length, needed for munmap
  29     const int prot; ///< mmap(2) "protection" flags
  30     const int flags; ///< other mmap(2) flags
  31     const off_t offset; ///< user-requested data offset
  32
  33     off_t delta; ///< mapped buffer increment to hit user offset
  34     void *buf; ///< buffer returned by mmap, needed for munmap
  35 };
  36
  37
  38 void *
  39 MmappedFile::operator new(size_t sz)
  40 {
  41     CBDATA_INIT_TYPE(MmappedFile);
  42     MmappedFile *result = cbdataAlloc(MmappedFile);
  43     /* Mark result as being owned - we want the refcounter to do the delete
  44      * call */
  45     return result;
  46 }
  47
  48 void
  49 MmappedFile::operator delete(void *address)
  50 {
  51     MmappedFile *t = static_cast<MmappedFile *>(address);
  52     cbdataFree(t);
  53 }
  54
  55 MmappedFile::MmappedFile(char const *aPath): fd(-1),
  56         minOffset(0), maxOffset(-1), error_(false)
  57 {
  58     assert(aPath);
  59     path_ = xstrdup(aPath);
  60     debugs(79,5, HERE << this << ' ' << path_);
  61 }
  62
  63 MmappedFile::~MmappedFile()
  64 {
  65     safe_free(path_);
  66     doClose();
  67 }
  68
  69 // XXX: almost a copy of BlockingFile::open
  70 void
  71 MmappedFile::open(int flags, mode_t mode, RefCount<IORequestor> callback)
  72 {
  73     assert(fd < 0);
  74
  75     /* Simulate async calls */
  76     fd = file_open(path_ , flags);
  77     ioRequestor = callback;
  78
  79     if (fd < 0) {
  80         debugs(79,3, HERE << "open error: " << xstrerror());
  81         error_ = true;
  82     } else {
  83         store_open_disk_fd++;
  84         debugs(79,3, HERE << "FD " << fd);
  85
  86         // setup mapping boundaries
  87         struct stat sb;
  88         if (fstat(fd, &sb) == 0)
  89             maxOffset = sb.st_size; // we do not expect it to change
  90     }
  91
  92     callback->ioCompletedNotification();
  93 }
  94
  95 /**
  96  * Alias for MmappedFile::open(...)
  97  \copydoc MmappedFile::open(int flags, mode_t mode, RefCount<IORequestor> callback)
  98  */
  99 void
 100 MmappedFile::create(int flags, mode_t mode, RefCount<IORequestor> callback)
 101 {
 102     /* We use the same logic path for open */
 103     open(flags, mode, callback);
 104 }
 105
 106 void MmappedFile::doClose()
 107 {
 108     if (fd >= 0) {
 109         file_close(fd);
 110         fd = -1;
 111         store_open_disk_fd--;
 112     }
 113 }
 114
 115 void
 116 MmappedFile::close()
 117 {
 118     debugs(79, 3, HERE << this << " closing for " << ioRequestor);
 119     doClose();
 120     assert(ioRequestor != NULL);
 121     ioRequestor->closeCompleted();
 122 }
 123
 124 bool
 125 MmappedFile::canRead() const
 126 {
 127     return fd >= 0;
 128 }
 129
 130 bool
 131 MmappedFile::canWrite() const
 132 {
 133     return fd >= 0;
 134 }
 135
 136 bool
 137 MmappedFile::error() const
 138 {
 139     return error_;
 140 }
 141
 142 void
 143 MmappedFile::read(ReadRequest *aRequest)
 144 {
 145     debugs(79,3, HERE << "(FD " << fd << ", " << aRequest->len << ", " <<
 146            aRequest->offset << ")");
 147
 148     assert(fd >= 0);
 149     assert(ioRequestor != NULL);
 150     assert(aRequest->len >= 0);
 151     assert(aRequest->len > 0); // TODO: work around mmap failures on zero-len?
 152     assert(aRequest->offset >= 0);
 153     assert(!error_); // TODO: propagate instead?
 154
 155     assert(minOffset < 0 || minOffset <= aRequest->offset);
 156     assert(maxOffset < 0 || static_cast<uint64_t>(aRequest->offset + aRequest->len) <= static_cast<uint64_t>(maxOffset));
 157
 158     Mmapping mapping(fd, aRequest->len, PROT_READ, MAP_PRIVATE | MAP_NORESERVE,
 159                      aRequest->offset);
 160
 161     bool done = false;
 162     if (void *buf = mapping.map()) {
 163         memcpy(aRequest->buf, buf, aRequest->len);
 164         done = mapping.unmap();
 165     }
 166     error_ = !done;
 167
 168     const ssize_t rlen = error_ ? -1 : (ssize_t)aRequest->len;
 169     const int errflag = error_ ? DISK_ERROR :DISK_OK;
 170     ioRequestor->readCompleted(aRequest->buf, rlen, errflag, aRequest);
 171 }
 172
 173 void
 174 MmappedFile::write(WriteRequest *aRequest)
 175 {
 176     debugs(79,3, HERE << "(FD " << fd << ", " << aRequest->len << ", " <<
 177            aRequest->offset << ")");
 178
 179     assert(fd >= 0);
 180     assert(ioRequestor != NULL);
 181     assert(aRequest->len >= 0);
 182     assert(aRequest->len > 0); // TODO: work around mmap failures on zero-len?
 183     assert(aRequest->offset >= 0);
 184     assert(!error_); // TODO: propagate instead?
 185
 186     assert(minOffset < 0 || minOffset <= aRequest->offset);
 187     assert(maxOffset < 0 || static_cast<uint64_t>(aRequest->offset + aRequest->len) <= static_cast<uint64_t>(maxOffset));
 188
 189     const ssize_t written =
 190         pwrite(fd, aRequest->buf, aRequest->len, aRequest->offset);
 191     if (written < 0) {
 192         debugs(79,1, HERE << "error: " << xstrerr(errno));
 193         error_ = true;
 194     } else if (static_cast<size_t>(written) != aRequest->len) {
 195         debugs(79,1, HERE << "problem: " << written << " < " << aRequest->len);
 196         error_ = true;
 197     }
 198
 199     if (aRequest->free_func)
 200         (aRequest->free_func)(const_cast<char*>(aRequest->buf)); // broken API?
 201
 202     if (!error_) {
 203         debugs(79,5, HERE << "wrote " << aRequest->len << " to FD " << fd << " at " << aRequest->offset);
 204     } else {
 205         doClose();
 206     }
 207
 208     const ssize_t rlen = error_ ? 0 : (ssize_t)aRequest->len;
 209     const int errflag = error_ ? DISK_ERROR :DISK_OK;
 210     ioRequestor->writeCompleted(errflag, rlen, aRequest);
 211 }
 212
 213 /// we only support blocking I/O
 214 bool
 215 MmappedFile::ioInProgress() const
 216 {
 217     return false;
 218 }
 219
 220 Mmapping::Mmapping(int aFd, size_t aLength, int aProt, int aFlags, off_t anOffset):
 221         fd(aFd), length(aLength), prot(aProt), flags(aFlags), offset(anOffset),
 222         delta(-1), buf(NULL)
 223 {
 224 }
 225
 226 Mmapping::~Mmapping()
 227 {
 228     if (buf)
 229         unmap();
 230 }
 231
 232 void *
 233 Mmapping::map()
 234 {
 235     // mmap(2) requires that offset is a multiple of the page size
 236     static const int pageSize = getpagesize();
 237     delta = offset % pageSize;
 238
 239     buf = mmap(NULL, length + delta, prot, flags, fd, offset - delta);
 240
 241     if (buf == MAP_FAILED) {
 242         const int errNo = errno;
 243         debugs(79,3, HERE << "error FD " << fd << "mmap(" << length << '+' <<
 244                delta << ", " << offset << '-' << delta << "): " << xstrerr(errNo));
 245         buf = NULL;
 246         return NULL;
 247     }
 248
 249     return static_cast<char*>(buf) + delta;
 250 }
 251
 252 bool
 253 Mmapping::unmap()
 254 {
 255     debugs(79,9, HERE << "FD " << fd <<
 256            " munmap(" << buf << ", " << length << '+' << delta << ')');
 257
 258     if (!buf) // forgot or failed to map
 259         return false;
 260
 261     const bool error = munmap(buf, length + delta) != 0;
 262     if (error) {
 263         const int errNo = errno;
 264         debugs(79,3, HERE << "error FD " << fd <<
 265                " munmap(" << buf << ", " << length << '+' << delta << "): " <<
 266                "): " << xstrerr(errNo));
 267     }
 268     buf = NULL;
 269     return !error;
 270 }
 271
 272 // TODO: check MAP_NORESERVE, consider MAP_POPULATE and MAP_FIXED