[Sheepdog] [PATCH 1/2] use O_DSYNC instead of O_SYNC

[Christoph Hellwig]

Using O_DSYNC means we do not have to write out the inode if we are
overwriting full allocated blocks.  For sheepdog that is a fairly usual
use case when blocks in an image has already been allocated and the guest
OS overwrites previously deleted blocks with new data.

Signed-off-by: Christoph Hellwig <hch at lst.de>

Index: sheepdog/sheep/journal.c
===================================================================
--- sheepdog.orig/sheep/journal.c	2011-11-10 21:24:20.851800458 +0100
+++ sheepdog/sheep/journal.c	2011-11-10 21:24:29.227795709 +0100
@@ -65,7 +65,7 @@ static int jrnl_close(struct jrnl_descri
 static int jrnl_create(struct jrnl_descriptor *jd, const char *jrnl_dir)
 {
 	snprintf(jd->path, sizeof(jd->path), "%sXXXXXX", jrnl_dir);
-	jd->fd = mkostemp(jd->path, O_SYNC);
+	jd->fd = mkostemp(jd->path, O_DSYNC);
 
 	if (jd->fd < 0) {
 		eprintf("failed to create %s: %m\n", jd->path);
@@ -283,7 +283,7 @@ int jrnl_recover(const char *jrnl_dir)
 		}
 		if (!jrnl_has_end_mark(&jd))
 			goto end_while_2;
-		jd.target_fd = open(jd.head.target_path, O_SYNC | O_RDWR);
+		jd.target_fd = open(jd.head.target_path, O_DSYNC | O_RDWR);
 		if (ret) {
 			eprintf("unable to open the object file %s for recovery\n",
 				jd.head.target_path);
Index: sheepdog/sheep/store.c
===================================================================
--- sheepdog.orig/sheep/store.c	2011-11-10 21:24:20.871799279 +0100
+++ sheepdog/sheep/store.c	2011-11-10 21:24:45.804065749 +0100
@@ -439,7 +439,7 @@ static int ob_open(uint32_t epoch, uint6
 	if (sys->use_directio && is_data_obj(oid))
 		flags = O_DIRECT | O_RDWR | aflags;
 	else
-		flags = O_SYNC | O_RDWR | aflags;
+		flags = O_DSYNC | O_RDWR | aflags;
 
 	snprintf(path, sizeof(path), "%s%08u/%016" PRIx64, obj_path, epoch, oid);
 
@@ -482,7 +482,7 @@ int update_epoch_log(int epoch)
 	dprintf("update epoch: %d, %d\n", epoch, sys->nr_nodes);
 
 	snprintf(path, sizeof(path), "%s%08u", epoch_path, epoch);
-	fd = open(path, O_RDWR | O_CREAT | O_SYNC, def_fmode);
+	fd = open(path, O_RDWR | O_CREAT | O_DSYNC, def_fmode);
 	if (fd < 0) {
 		ret = fd;
 		goto err_open;
@@ -1008,7 +1008,7 @@ int set_cluster_ctime(uint64_t ct)
 {
 	int fd, ret;
 
-	fd = open(config_path, O_SYNC | O_WRONLY);
+	fd = open(config_path, O_DSYNC | O_WRONLY);
 	if (fd < 0)
 		return -1;
 
@@ -1310,7 +1310,7 @@ next:
 
 	if (rsp->result == SD_RES_SUCCESS) {
 		char path[PATH_MAX], tmp_path[PATH_MAX];
-		int flags = O_SYNC | O_RDWR | O_CREAT;
+		int flags = O_DSYNC | O_RDWR | O_CREAT;
 
 		snprintf(path, sizeof(path), "%s%08u/%016" PRIx64, obj_path,
 			 epoch, oid);
@@ -2043,7 +2043,7 @@ int set_cluster_copies(uint8_t copies)
 {
 	int fd, ret;
 
-	fd = open(config_path, O_SYNC | O_WRONLY);
+	fd = open(config_path, O_DSYNC | O_WRONLY);
 	if (fd < 0)
 		return SD_RES_EIO;
 
@@ -2080,7 +2080,7 @@ int set_cluster_flags(uint16_t flags)
 {
 	int fd, ret = SD_RES_EIO;
 
-	fd = open(config_path, O_SYNC | O_WRONLY);
+	fd = open(config_path, O_DSYNC | O_WRONLY);
 	if (fd < 0)
 		goto out;