On unix, always use fdatasync() instead of fsync() when available, even if

the file size changes, since (we are told) fdatasync() will automatically
flush the inode when the file size changes. (CVS 6367)

FossilOrigin-Name: 0d6b11bcf67f86e5554806869d32338e5831833e

diff --git a/manifest b/manifest
index c691926fa64f2d85747cd184f2356e2bb2565052..5e6e4735b3f9bc7625c46a730137f7d110d0fdc0 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sa\stest\sto\stry\sto\shit\sthe\srace-condition\sfixed\sby\s(6363).\s(CVS\s6366)
-D 2009-03-20T15:16:06
+C On\sunix,\salways\suse\sfdatasync()\sinstead\sof\sfsync()\swhen\savailable,\seven\sif\nthe\sfile\ssize\schanges,\ssince\s(we\sare\stold)\sfdatasync()\swill\sautomatically\nflush\sthe\sinode\swhen\sthe\sfile\ssize\schanges.\s(CVS\s6367)
+D 2009-03-21T14:41:04
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 583e87706abc3026960ed759aff6371faf84c211
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -141,7 +141,7 @@ F src/os.c ed93a6b46132a602c4fd7a58142e2981c829c79d
 F src/os.h fa3f4aa0119ff721a2da4b47ffd74406ac864c05
 F src/os_common.h 8c61457df58f1a4bd5f5adc3e90e01b37bf7afbc
 F src/os_os2.c bed77dc26e3a95ce4a204936b9a1ca6fe612fcc5
-F src/os_unix.c 52352674c19688026a72cd0e8620e6a29bacba4a
+F src/os_unix.c 8f6ffa95c8dc79b94565b517bc37abb426f09a23
 F src/os_win.c 40636702058ed4dcd35d68151bfab56d4997cdc1
 F src/pager.c 01e3facb2f7c5f307e36a0f4ed9343cf3761711a
 F src/pager.h 0c9f3520c00d8a3b8e792ca56c9a11b6b02b4b0f
@@ -709,7 +709,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P a08324d16d1e9a4e7c1b294bc71fc939d173f826
-R 87fff081bb6bfc825b1acb6eabea142e
-U danielk1977
-Z 5f0bd3312fbc59ec4534315ac49a7c31
+P 4310411f5027dba18e017023e21cb09982e26752
+R da4300d409cda801b0b75c2eee2c6174
+U drh
+Z 669efac6174bfcb881ee9f0e80879f8c

diff --git a/manifest.uuid b/manifest.uuid
index 259c523a022359869365c078fd38a39647be1cc4..d343d63b425c243e4abd6dfba9822ea42b99f746 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-4310411f5027dba18e017023e21cb09982e26752
\ No newline at end of file
+0d6b11bcf67f86e5554806869d32338e5831833e
\ No newline at end of file

diff --git a/src/os_unix.c b/src/os_unix.c
index e21a59b15c14c9b60faeb135b9567e5e4b3efd80..ec781a5568ca9e7ae8b629e005aa1bd53eeb9b14 100644 (file)
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -43,7 +43,7 @@
 **   *  Definitions of sqlite3_vfs objects for all locking methods
 **      plus implementations of sqlite3_os_init() and sqlite3_os_end().
 **
-** $Id: os_unix.c,v 1.242 2009/03/01 22:29:20 drh Exp $
+** $Id: os_unix.c,v 1.243 2009/03/21 14:41:04 drh Exp $
 */
 #include "sqliteInt.h"
 #if SQLITE_OS_UNIX              /* This file is used on unix only */
@@ -2853,6 +2853,19 @@ int sqlite3_fullsync_count = 0;
 ** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
 ** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
 ** or power failure will likely corrupt the database file.
+**
+** SQLite sets the dataOnly flag if the size of the file is unchanged.
+** The idea behind dataOnly is that it should only write the file content
+** to disk, not the inode.  We only set dataOnly if the file size is 
+** unchanged since the file size is part of the inode.  However, 
+** Ted Ts'o tells us that fdatasync() will also write the inode if the
+** file size has changed.  The only real difference between fdatasync()
+** and fsync(), Ted tells us, is that fdatasync() will not flush the
+** inode if the mtime or owner or other inode attributes have changed.
+** We only care about the file size, not the other file attributes, so
+** as far as SQLite is concerned, an fdatasync() is always adequate.
+** So, we always use fdatasync() if it is available, regardless of
+** the value of the dataOnly flag.
 */
 static int full_fsync(int fd, int fullSync, int dataOnly){
   int rc;
@@ -2869,6 +2882,7 @@ static int full_fsync(int fd, int fullSync, int dataOnly){
   UNUSED_PARAMETER(dataOnly);
 #else
   UNUSED_PARAMETER(fullSync);
+  UNUSED_PARAMETER(dataOnly);
 #endif
 
   /* Record the number of times that we do a normal fsync() and 
@@ -2902,16 +2916,12 @@ static int full_fsync(int fd, int fullSync, int dataOnly){
   if( rc ) rc = fsync(fd);
 
 #else 
-  if( dataOnly ){
-    rc = fdatasync(fd);
+  rc = fdatasync(fd);
 #if OS_VXWORKS
-    if( rc==-1 && errno==ENOTSUP ){
-      rc = fsync(fd);
-    }
-#endif
-  }else{
+  if( rc==-1 && errno==ENOTSUP ){
     rc = fsync(fd);
   }
+#endif /* OS_VXWORKS */
 #endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
 
   if( OS_VXWORKS && rc!= -1 ){