r3944: Fix the problem we get on Linux where sendfile fails, but we've already sent the
authorJeremy Allison <jra@samba.org>
Wed, 24 Nov 2004 22:05:59 +0000 (22:05 +0000)
committerGerald (Jerry) Carter <jerry@samba.org>
Wed, 10 Oct 2007 15:53:26 +0000 (10:53 -0500)
header using send(). As our implementation of sendfile can't return EINTR (it
restarts in that case) use an errno of EINTR to signal the linux sendfile fail
after header case. When that happens send the rest of the data and then turn
off sendfile. Sendfile should be safe to enable on all systems now (even though
it may not help in all performance cases).
Jeremy.

source/lib/sendfile.c
source/smbd/reply.c

index 4aa76a0c74ad728ae19104ac2fc52c0894bcb6c8..75fb635fa2613142029a1a5a84a1830fe1bfe458 100644 (file)
@@ -65,8 +65,20 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, SMB_OFF_T of
                        nwritten = sendfile(tofd, fromfd, &offset, total);
 #endif
                } while (nwritten == -1 && errno == EINTR);
-               if (nwritten == -1)
+               if (nwritten == -1) {
+                       if (errno == ENOSYS) {
+                               /* Ok - we're in a world of pain here. We just sent
+                                * the header, but the sendfile failed. We have to
+                                * emulate the sendfile at an upper layer before we
+                                * disable it's use. So we do something really ugly.
+                                * We set the errno to a strange value so we can detect
+                                * this at the upper level and take care of it without
+                                * layer violation. JRA.
+                                */
+                               errno = EINTR; /* Normally we can never return this. */
+                       }
                        return -1;
+               }
                if (nwritten == 0)
                        return -1; /* I think we're at EOF here... */
                total -= nwritten;
@@ -131,8 +143,20 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, SMB_OFF_T of
                do {
                        nwritten = sendfile(tofd, fromfd, &small_offset, small_total);
                } while (nwritten == -1 && errno == EINTR);
-               if (nwritten == -1)
+               if (nwritten == -1) {
+                       if (errno == ENOSYS) {
+                               /* Ok - we're in a world of pain here. We just sent
+                                * the header, but the sendfile failed. We have to
+                                * emulate the sendfile at an upper layer before we
+                                * disable it's use. So we do something really ugly.
+                                * We set the errno to a strange value so we can detect
+                                * this at the upper level and take care of it without
+                                * layer violation. JRA.
+                                */
+                               errno = EINTR; /* Normally we can never return this. */
+                       }
                        return -1;
+               }
                if (nwritten == 0)
                        return -1; /* I think we're at EOF here... */
                small_total -= nwritten;
index a3bb41257859aae9a5b2437425f6b248aed099f7..f8f6a14067495b24f330408749624444e0bcbedc 100644 (file)
@@ -1717,7 +1717,7 @@ int reply_unlink(connection_struct *conn, char *inbuf,char *outbuf, int dum_size
  Fail for readbraw.
 ****************************************************************************/
 
-void fail_readraw(void)
+static void fail_readraw(void)
 {
        pstring errstr;
        slprintf(errstr, sizeof(errstr)-1, "FAIL ! reply_readbraw: socket write fail (%s)",
@@ -1725,12 +1725,46 @@ void fail_readraw(void)
        exit_server(errstr);
 }
 
+#if defined(WITH_SENDFILE)
+/****************************************************************************
+ Fake (read/write) sendfile. Returns -1 on read or write fail.
+****************************************************************************/
+
+static ssize_t fake_sendfile(files_struct *fsp, SMB_OFF_T startpos, size_t nread, char *buf, int bufsize)
+{
+       ssize_t ret=0;
+
+       /* Paranioa check... */
+       if (nread > bufsize) {
+               fail_readraw();
+       }
+
+       if (nread > 0) {
+               ret = read_file(fsp,buf,startpos,nread);
+               if (ret == -1) {
+                       return -1;
+               }
+       }
+
+       /* If we had a short read, fill with zeros. */
+       if (ret < nread) {
+               memset(buf, '\0', nread - ret);
+       }
+
+       if (write_data(smbd_server_fd(),buf,nread) != nread) {
+               return -1;
+       }       
+
+       return (ssize_t)nread;
+}
+#endif
+
 /****************************************************************************
  Use sendfile in readbraw.
 ****************************************************************************/
 
 void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T startpos, size_t nread,
-               ssize_t mincount, char *outbuf)
+               ssize_t mincount, char *outbuf, int out_buffsize)
 {
        ssize_t ret=0;
 
@@ -1752,12 +1786,21 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
 
                if ( SMB_VFS_SENDFILE( smbd_server_fd(), fsp, fsp->fd, &header, startpos, nread) == -1) {
                        /*
-                        * Special hack for broken Linux with no 64 bit clean sendfile. If we
-                        * return ENOSYS then pretend we just got a normal read.
+                        * Special hack for broken Linux with no working sendfile. If we
+                        * return EINTR we sent the header but not the rest of the data.
+                        * Fake this up by doing read/write calls.
                         */
-                       if (errno == ENOSYS) {
+                       if (errno == EINTR) {
+                               /* Ensure we don't do this again. */
                                set_use_sendfile(SNUM(conn), False);
-                               goto normal_read;
+                               DEBUG(0,("send_file_readbraw: sendfile not available. Faking..\n"));
+
+                               if (fake_sendfile(fsp, startpos, nread, outbuf + 4, out_buffsize - 4) == -1) {
+                                       DEBUG(0,("send_file_readbraw: fake_sendfile failed for file %s (%s).\n",
+                                               fsp->fsp_name, strerror(errno) ));
+                                       exit_server("send_file_readbraw fake_sendfile failed");
+                               }
+                               return;
                        }
 
                        DEBUG(0,("send_file_readbraw: sendfile failed for file %s (%s). Terminating\n",
@@ -1767,7 +1810,6 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
 
        }
 
-  normal_read:
 #endif
 
        if (nread > 0) {
@@ -1790,7 +1832,7 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
  Reply to a readbraw (core+ protocol).
 ****************************************************************************/
 
-int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_size, int dum_buffsize)
+int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_size, int out_buffsize)
 {
        extern struct current_user current_user;
        ssize_t maxcount,mincount;
@@ -1905,7 +1947,7 @@ int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_s
        DEBUG( 3, ( "readbraw fnum=%d start=%.0f max=%d min=%d nread=%d\n", fsp->fnum, (double)startpos,
                                (int)maxcount, (int)mincount, (int)nread ) );
   
-       send_file_readbraw(conn, fsp, startpos, nread, mincount, outbuf);
+       send_file_readbraw(conn, fsp, startpos, nread, mincount, outbuf, out_buffsize);
 
        DEBUG(5,("readbraw finished\n"));
        END_PROFILE(SMBreadbraw);
@@ -2069,7 +2111,7 @@ Returning short read of maximum allowed for compatibility with Windows 2000.\n",
  Reply to a read and X - possibly using sendfile.
 ****************************************************************************/
 
-int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length, 
+int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length, int len_outbuf,
                files_struct *fsp, SMB_OFF_T startpos, size_t smb_maxcnt)
 {
        ssize_t nread = -1;
@@ -2117,12 +2159,22 @@ int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length
 
                if ( SMB_VFS_SENDFILE( smbd_server_fd(), fsp, fsp->fd, &header, startpos, smb_maxcnt) == -1) {
                        /*
-                        * Special hack for broken Linux with no 64 bit clean sendfile. If we
-                        * return ENOSYS then pretend we just got a normal read.
+                        * Special hack for broken Linux with no working sendfile. If we
+                        * return EINTR we sent the header but not the rest of the data.
+                        * Fake this up by doing read/write calls.
                         */
-                       if (errno == ENOSYS) {
+                       if (errno == EINTR) {
+                               /* Ensure we don't do this again. */
                                set_use_sendfile(SNUM(conn), False);
-                               goto normal_read;
+                               DEBUG(0,("send_file_readX: sendfile not available. Faking..\n"));
+
+                               if ((nread = fake_sendfile(fsp, startpos, smb_maxcnt, data,
+                                                       len_outbuf - (data-outbuf))) == -1) {
+                                       DEBUG(0,("send_file_readX: fake_sendfile failed for file %s (%s).\n",
+                                               fsp->fsp_name, strerror(errno) ));
+                                       exit_server("send_file_readX: fake_sendfile failed");
+                               }
+                               return nread;
                        }
 
                        DEBUG(0,("send_file_readX: sendfile failed for file %s (%s). Terminating\n",
@@ -2223,7 +2275,7 @@ int reply_read_and_X(connection_struct *conn, char *inbuf,char *outbuf,int lengt
                return ERROR_DOS(ERRDOS,ERRlock);
        }
 
-       nread = send_file_readX(conn, inbuf, outbuf, length, fsp, startpos, smb_maxcnt);
+       nread = send_file_readX(conn, inbuf, outbuf, length, bufsize, fsp, startpos, smb_maxcnt);
        if (nread != -1)
                nread = chain_reply(inbuf,outbuf,length,bufsize);