[gfs2-utils] 01/02: gfs2_jadd: Use fallocate to preallocate journals

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andyp pushed a commit to branch master
in repository gfs2-utils.

commit 2010383c860ef8ca2a80e6394b9cb89942a426e0
Author: Andrew Price 
AuthorDate: Thu Mar 18 17:30:53 2021 +0000

gfs2_jadd: Use fallocate to preallocate journals

Fall back to writes for ancient kernels and use larger writes in that
    case to reduce the chance of fragmentation.

Signed-off-by: Andrew Price 
---
 gfs2/mkfs/main_jadd.c | 48 ++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 40 insertions(+), 8 deletions(-)

diff --git a/gfs2/mkfs/main_jadd.c b/gfs2/mkfs/main_jadd.c
index 7583ba0f..0a18bfb2 100644
--- a/gfs2/mkfs/main_jadd.c
+++ b/gfs2/mkfs/main_jadd.c
@@ -480,6 +480,43 @@ static uint64_t find_block_address(int fd, off_t offset, unsigned bsize)
 }
 #endif

+static int alloc_new_journal(int fd, unsigned bytes)
+{
+#define ALLOC_BUF_SIZE (4 << 20)
+	unsigned left = bytes;
+	int error;
+	char *buf;
+
+	error = fallocate(fd, 0, 0, bytes);
+	if (error == 0)
+	       return 0;
+	if (errno != EOPNOTSUPP)
+		goto out_errno;
+
+	/* No fallocate support, fall back to writes */
+	buf = calloc(1, ALLOC_BUF_SIZE);
+	if (buf == NULL)
+		goto out_errno;
+
+	while (left > 0) {
+		unsigned sz = ALLOC_BUF_SIZE;
+
+		if (left < ALLOC_BUF_SIZE)
+			sz = left;
+
+		if (pwrite(fd, buf, sz, bytes - left) != sz) {
+			free(buf);
+			goto out_errno;
+		}
+		left -= sz;
+	}
+	free(buf);
+	return 0;
+out_errno:
+	perror("Failed to allocate space for new journal");
+	return -1;
+}
+
 static int add_j(struct gfs2_sbd *sdp, struct jadd_opts *opts)
 {
    int fd, error = 0;
@@ -496,14 +533,9 @@ static int add_j(struct gfs2_sbd *sdp, struct jadd_opts *opts)
    if ((error = set_flags(fd, JA_FL_CLEAR, FS_JOURNAL_DATA_FL)))
    	goto close_fd;

-	memset(buf, 0, sdp->bsize);
-	for (x=0; x<blocks; x++) {
-		if (write(fd, buf, sdp->bsize) != sdp->bsize) {
-			perror("add_j write");
-			error = -1;
-			goto close_fd;
-		}
-	}
+	error = alloc_new_journal(fd, sdp->jsize << 20);
+	if (error != 0)
+		goto close_fd;

if ((error = lseek(fd, 0, SEEK_SET)) < 0) {
    	perror("add_j lseek");