src/DiskIO/Mmapped/MmappedFile.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 47    Store Directory Routines
   5  */
   6
   7 #include "squid.h"
   8 #include "Debug.h"
   9 #include "DiskIO/IORequestor.h"
  10 #include "DiskIO/Mmapped/MmappedFile.h"
  11 #include "DiskIO/ReadRequest.h"
  12 #include "DiskIO/WriteRequest.h"
  13 #include "disk.h"
  14 #include "globals.h"
  15 #include "protos.h"
  16
  17 #if HAVE_SYS_MMAN_H
  18 #include <sys/mman.h>
  19 #endif
  20 #if HAVE_SYS_STAT_H
  21 #include <sys/stat.h>
  22 #endif
  23 #if HAVE_ERRNO_H
  24 #include <errno.h>
  25 #endif
  26
  27 CBDATA_CLASS_INIT(MmappedFile);
  28
  29 // helper class to deal with mmap(2) offset alignment and other low-level specs
  30 class Mmapping
  31 {
  32 public:
  33     Mmapping(int fd, size_t length, int prot, int flags, off_t offset);
  34     ~Mmapping();
  35
  36     void *map(); ///< calls mmap(2); returns usable buffer or nil on failure
  37     bool unmap(); ///< unmaps previously mapped buffer, if any
  38
  39 private:
  40     const int fd; ///< descriptor of the mmapped file
  41     const size_t length; ///< user-requested data length, needed for munmap
  42     const int prot; ///< mmap(2) "protection" flags
  43     const int flags; ///< other mmap(2) flags
  44     const off_t offset; ///< user-requested data offset
  45
  46     off_t delta; ///< mapped buffer increment to hit user offset
  47     void *buf; ///< buffer returned by mmap, needed for munmap
  48 };
  49
  50 void *
  51 MmappedFile::operator new(size_t sz)
  52 {
  53     CBDATA_INIT_TYPE(MmappedFile);
  54     MmappedFile *result = cbdataAlloc(MmappedFile);
  55     /* Mark result as being owned - we want the refcounter to do the delete
  56      * call */
  57     return result;
  58 }
  59
  60 void
  61 MmappedFile::operator delete(void *address)
  62 {
  63     MmappedFile *t = static_cast<MmappedFile *>(address);
  64     cbdataFree(t);
  65 }
  66
  67 MmappedFile::MmappedFile(char const *aPath): fd(-1),
  68         minOffset(0), maxOffset(-1), error_(false)
  69 {
  70     assert(aPath);
  71     path_ = xstrdup(aPath);
  72     debugs(79,5, HERE << this << ' ' << path_);
  73 }
  74
  75 MmappedFile::~MmappedFile()
  76 {
  77     safe_free(path_);
  78     doClose();
  79 }
  80
  81 // XXX: almost a copy of BlockingFile::open
  82 void
  83 MmappedFile::open(int flags, mode_t mode, RefCount<IORequestor> callback)
  84 {
  85     assert(fd < 0);
  86
  87     /* Simulate async calls */
  88     fd = file_open(path_ , flags);
  89     ioRequestor = callback;
  90
  91     if (fd < 0) {
  92         debugs(79,3, HERE << "open error: " << xstrerror());
  93         error_ = true;
  94     } else {
  95         ++store_open_disk_fd;
  96         debugs(79,3, HERE << "FD " << fd);
  97
  98         // setup mapping boundaries
  99         struct stat sb;
 100         if (fstat(fd, &sb) == 0)
 101             maxOffset = sb.st_size; // we do not expect it to change
 102     }
 103
 104     callback->ioCompletedNotification();
 105 }
 106
 107 /**
 108  * Alias for MmappedFile::open(...)
 109  \copydoc MmappedFile::open(int flags, mode_t mode, RefCount<IORequestor> callback)
 110  */
 111 void
 112 MmappedFile::create(int flags, mode_t mode, RefCount<IORequestor> callback)
 113 {
 114     /* We use the same logic path for open */
 115     open(flags, mode, callback);
 116 }
 117
 118 void MmappedFile::doClose()
 119 {
 120     if (fd >= 0) {
 121         file_close(fd);
 122         fd = -1;
 123         --store_open_disk_fd;
 124     }
 125 }
 126
 127 void
 128 MmappedFile::close()
 129 {
 130     debugs(79, 3, HERE << this << " closing for " << ioRequestor);
 131     doClose();
 132     assert(ioRequestor != NULL);
 133     ioRequestor->closeCompleted();
 134 }
 135
 136 bool
 137 MmappedFile::canRead() const
 138 {
 139     return fd >= 0;
 140 }
 141
 142 bool
 143 MmappedFile::canWrite() const
 144 {
 145     return fd >= 0;
 146 }
 147
 148 bool
 149 MmappedFile::error() const
 150 {
 151     return error_;
 152 }
 153
 154 void
 155 MmappedFile::read(ReadRequest *aRequest)
 156 {
 157     debugs(79,3, HERE << "(FD " << fd << ", " << aRequest->len << ", " <<
 158            aRequest->offset << ")");
 159
 160     assert(fd >= 0);
 161     assert(ioRequestor != NULL);
 162     assert(aRequest->len > 0); // TODO: work around mmap failures on zero-len?
 163     assert(aRequest->offset >= 0);
 164     assert(!error_); // TODO: propagate instead?
 165
 166     assert(minOffset < 0 || minOffset <= aRequest->offset);
 167     assert(maxOffset < 0 || static_cast<uint64_t>(aRequest->offset + aRequest->len) <= static_cast<uint64_t>(maxOffset));
 168
 169     Mmapping mapping(fd, aRequest->len, PROT_READ, MAP_PRIVATE | MAP_NORESERVE,
 170                      aRequest->offset);
 171
 172     bool done = false;
 173     if (void *buf = mapping.map()) {
 174         memcpy(aRequest->buf, buf, aRequest->len);
 175         done = mapping.unmap();
 176     }
 177     error_ = !done;
 178
 179     const ssize_t rlen = error_ ? -1 : (ssize_t)aRequest->len;
 180     const int errflag = error_ ? DISK_ERROR :DISK_OK;
 181     ioRequestor->readCompleted(aRequest->buf, rlen, errflag, aRequest);
 182 }
 183
 184 void
 185 MmappedFile::write(WriteRequest *aRequest)
 186 {
 187     debugs(79,3, HERE << "(FD " << fd << ", " << aRequest->len << ", " <<
 188            aRequest->offset << ")");
 189
 190     assert(fd >= 0);
 191     assert(ioRequestor != NULL);
 192     assert(aRequest->len > 0); // TODO: work around mmap failures on zero-len?
 193     assert(aRequest->offset >= 0);
 194     assert(!error_); // TODO: propagate instead?
 195
 196     assert(minOffset < 0 || minOffset <= aRequest->offset);
 197     assert(maxOffset < 0 || static_cast<uint64_t>(aRequest->offset + aRequest->len) <= static_cast<uint64_t>(maxOffset));
 198
 199     const ssize_t written =
 200         pwrite(fd, aRequest->buf, aRequest->len, aRequest->offset);
 201     if (written < 0) {
 202         debugs(79, DBG_IMPORTANT, HERE << "error: " << xstrerr(errno));
 203         error_ = true;
 204     } else if (static_cast<size_t>(written) != aRequest->len) {
 205         debugs(79, DBG_IMPORTANT, HERE << "problem: " << written << " < " << aRequest->len);
 206         error_ = true;
 207     }
 208
 209     if (aRequest->free_func)
 210         (aRequest->free_func)(const_cast<char*>(aRequest->buf)); // broken API?
 211
 212     if (!error_) {
 213         debugs(79,5, HERE << "wrote " << aRequest->len << " to FD " << fd << " at " << aRequest->offset);
 214     } else {
 215         doClose();
 216     }
 217
 218     const ssize_t rlen = error_ ? 0 : (ssize_t)aRequest->len;
 219     const int errflag = error_ ? DISK_ERROR :DISK_OK;
 220     ioRequestor->writeCompleted(errflag, rlen, aRequest);
 221 }
 222
 223 /// we only support blocking I/O
 224 bool
 225 MmappedFile::ioInProgress() const
 226 {
 227     return false;
 228 }
 229
 230 Mmapping::Mmapping(int aFd, size_t aLength, int aProt, int aFlags, off_t anOffset):
 231         fd(aFd), length(aLength), prot(aProt), flags(aFlags), offset(anOffset),
 232         delta(-1), buf(NULL)
 233 {
 234 }
 235
 236 Mmapping::~Mmapping()
 237 {
 238     if (buf)
 239         unmap();
 240 }
 241
 242 void *
 243 Mmapping::map()
 244 {
 245     // mmap(2) requires that offset is a multiple of the page size
 246     static const int pageSize = getpagesize();
 247     delta = offset % pageSize;
 248
 249     buf = mmap(NULL, length + delta, prot, flags, fd, offset - delta);
 250
 251     if (buf == MAP_FAILED) {
 252         const int errNo = errno;
 253         debugs(79,3, HERE << "error FD " << fd << "mmap(" << length << '+' <<
 254                delta << ", " << offset << '-' << delta << "): " << xstrerr(errNo));
 255         buf = NULL;
 256         return NULL;
 257     }
 258
 259     return static_cast<char*>(buf) + delta;
 260 }
 261
 262 bool
 263 Mmapping::unmap()
 264 {
 265     debugs(79,9, HERE << "FD " << fd <<
 266            " munmap(" << buf << ", " << length << '+' << delta << ')');
 267
 268     if (!buf) // forgot or failed to map
 269         return false;
 270
 271     const bool error = munmap(buf, length + delta) != 0;
 272     if (error) {
 273         const int errNo = errno;
 274         debugs(79,3, HERE << "error FD " << fd <<
 275                " munmap(" << buf << ", " << length << '+' << delta << "): " <<
 276                "): " << xstrerr(errNo));
 277     }
 278     buf = NULL;
 279     return !error;
 280 }
 281
 282 // TODO: check MAP_NORESERVE, consider MAP_POPULATE and MAP_FIXED