From 1f3de3f0e20d20e8f388f07339630090edaba56c Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 16 Mar 2018 10:07:07 +0100
Subject: [SERVER] Make sparse file mode actually work

---
 src/server/fileutil.c | 15 +++++++++++----
 src/server/fileutil.h |  1 +
 src/server/image.c    | 17 ++++++++++++-----
 3 files changed, 24 insertions(+), 9 deletions(-)

(limited to 'src/server')

diff --git a/src/server/fileutil.c b/src/server/fileutil.c
index d41dc85..336ab68 100644
--- a/src/server/fileutil.c
+++ b/src/server/fileutil.c
@@ -58,11 +58,18 @@ bool file_alloc(int fd, uint64_t offset, uint64_t size)
 #elif defined(__FreeBSD__)
 	if ( posix_fallocate( fd, offset, size ) == 0 ) return true; // slow way
 #endif
+	return false;
+}
+
+bool file_setSize(int fd, uint64_t size)
+{
+	if ( ftruncate( fd, size ) == 0 ) return true;
 
-	/* This doesn't make any sense, AFAIK
-	if ( lseek( fd, offset + size - 1, SEEK_SET ) != (off_t)offset ) return false; // dumb way
-	if ( write( fd, "", 1 ) != 1 ) return false;
-	*/
+	// Try really hard... image loading logic relies on the file
+	// having the proper apparent size
+	uint8_t byte = 0;
+	pread( fd, &byte, 1, size - 1 );
+	if ( pwrite( fd, &byte, 1, size - 1 ) == 1 ) return true;
 	return false;
 }
 
diff --git a/src/server/fileutil.h b/src/server/fileutil.h
index a4458a3..fcb5c20 100644
--- a/src/server/fileutil.h
+++ b/src/server/fileutil.h
@@ -9,6 +9,7 @@ bool file_isReadable(char *file);
 bool file_isWritable(char *file);
 bool mkdir_p(const char* path);
 bool file_alloc(int fd, uint64_t offset, uint64_t size);
+bool file_setSize(int fd, uint64_t size);
 bool file_freeDiskSpace(const char * const path, uint64_t *total, uint64_t *avail);
 time_t file_lastModification(const char * const file);
 int file_loadLineBased(const char * const file, int minFields, int maxFields, void (*cb)(int argc, char **argv, void *data), void *data);
diff --git a/src/server/image.c b/src/server/image.c
index 78091f1..cb01181 100644
--- a/src/server/image.c
+++ b/src/server/image.c
@@ -1123,19 +1123,22 @@ bool image_create(char *image, int revision, uint64_t size)
 		goto failure_cleanup;
 	}
 	// Try cache map first
-	if ( !file_alloc( fdCache, 0, mapsize ) ) {
+	if ( !file_alloc( fdCache, 0, mapsize ) && !file_setSize( fdCache, mapsize ) ) {
 		const int err = errno;
 		logadd( LOG_DEBUG1, "Could not allocate %d bytes for %s (errno=%d)", mapsize, cache, err );
 	}
 	// Now write image
 	if ( !_sparseFiles && !file_alloc( fdImage, 0, size ) ) {
-		const int err = errno;
-		logadd( LOG_ERROR, "Could not allocate %" PRIu64 " bytes for %s (errno=%d)", size, path, err );
+		logadd( LOG_ERROR, "Could not allocate %" PRIu64 " bytes for %s (errno=%d)", size, path, errno );
 		logadd( LOG_ERROR, "It is highly recommended to use a file system that supports preallocating disk"
 				" space without actually writing all zeroes to the block device." );
 		logadd( LOG_ERROR, "If you cannot fix this, try setting sparseFiles=true, but don't expect"
 				" divine performance during replication." );
 		goto failure_cleanup;
+	} else if ( _sparseFiles && !file_setSize( fdImage, size ) ) {
+		logadd( LOG_ERROR, "Could not create sparse file of %" PRIu64 " bytes for %s (errno=%d)", size, path, errno );
+		logadd( LOG_ERROR, "Make sure you have enough disk space, check directory permissions, fs errors etc." );
+		goto failure_cleanup;
 	}
 	close( fdImage );
 	close( fdCache );
@@ -1741,8 +1744,12 @@ static bool image_ensureDiskSpace(uint64_t size, bool force)
 			current = image_release( current );
 		}
 		declare_now;
-		if ( oldest == NULL || timing_diff( &oldest->atime, &now ) < 86400 ) {
-			logadd( LOG_DEBUG1, "No image is old enough (all have been in use in past 24h) :-(\n" );
+		if ( oldest == NULL || ( !_sparseFiles && timing_diff( &oldest->atime, &now ) < 86400 ) ) {
+			if ( oldest == NULL ) {
+				logadd( LOG_INFO, "All images are currently in use :-(" );
+			} else {
+				logadd( LOG_INFO, "Won't free any image, all have been in use in the past 24 hours :-(" );
+			}
 			return false;
 		}
 		oldest = image_lock( oldest );
-- 
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