pg_checksums: Handle read and write returns correctly

petere · petere · commit 1d7a6e3eb459 · 2019-09-03T08:30:21.000+02:00
The read() return was not checking for errors, the write() return was not checking for short writes. Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://www.postgresql.org/message-id/flat/5de61b6b-8be9-7771-0048-860328efe027%402ndquadrant.com
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
@@ -198,8 +198,12 @@ scan_file(const char *fn, BlockNumber segmentno)
 			break;
 		if (r != BLCKSZ)
 		{
-			pg_log_error("could not read block %u in file \"%s\": read %d of %d",
-						 blockno, fn, r, BLCKSZ);
+			if (r < 0)
+				pg_log_error("could not read block %u in file \"%s\": %m",
+							 blockno, fn);
+			else
+				pg_log_error("could not read block %u in file \"%s\": read %d of %d",
+							 blockno, fn, r, BLCKSZ);
 			exit(1);
 		}
 		blocks++;
@@ -222,6 +226,8 @@ scan_file(const char *fn, BlockNumber segmentno)
 		}
 		else if (mode == PG_MODE_ENABLE)
 		{
+			int		w;
+
 			/* Set checksum in page header */
 			header->pd_checksum = csum;
 
@@ -233,10 +239,15 @@ scan_file(const char *fn, BlockNumber segmentno)
 			}
 
 			/* Write block with checksum */
-			if (write(f, buf.data, BLCKSZ) != BLCKSZ)
+			w = write(f, buf.data, BLCKSZ);
+			if (w != BLCKSZ)
 			{
-				pg_log_error("could not write block %u in file \"%s\": %m",
-							 blockno, fn);
+				if (w < 0)
+					pg_log_error("could not write block %u in file \"%s\": %m",
+								 blockno, fn);
+				else
+					pg_log_error("could not write block %u in file \"%s\": wrote %d of %d",
+								 blockno, fn, w, BLCKSZ);
 				exit(1);
 			}
 		}

Original file line number	Diff line number	Diff line change
`@@ -198,8 +198,12 @@ scan_file(const char *fn, BlockNumber segmentno)`
`198`	`198`	`break;`
`199`	`199`	`if (r != BLCKSZ)`
`200`	`200`	`{`
`201`		`- pg_log_error("could not read block %u in file \"%s\": read %d of %d",`
`202`		`- blockno, fn, r, BLCKSZ);`
	`201`	`+ if (r < 0)`
	`202`	`+ pg_log_error("could not read block %u in file \"%s\": %m",`
	`203`	`+ blockno, fn);`
	`204`	`+ else`
	`205`	`+ pg_log_error("could not read block %u in file \"%s\": read %d of %d",`
	`206`	`+ blockno, fn, r, BLCKSZ);`
`203`	`207`	`exit(1);`
`204`	`208`	`}`
`205`	`209`	`blocks++;`
`@@ -222,6 +226,8 @@ scan_file(const char *fn, BlockNumber segmentno)`
`222`	`226`	`}`
`223`	`227`	`else if (mode == PG_MODE_ENABLE)`
`224`	`228`	`{`
	`229`	`+ int w;`
	`230`	`+`
`225`	`231`	`/* Set checksum in page header */`
`226`	`232`	`header->pd_checksum = csum;`
`227`	`233`
`@@ -233,10 +239,15 @@ scan_file(const char *fn, BlockNumber segmentno)`
`233`	`239`	`}`
`234`	`240`
`235`	`241`	`/* Write block with checksum */`
`236`		`- if (write(f, buf.data, BLCKSZ) != BLCKSZ)`
	`242`	`+ w = write(f, buf.data, BLCKSZ);`
	`243`	`+ if (w != BLCKSZ)`
`237`	`244`	`{`
`238`		`- pg_log_error("could not write block %u in file \"%s\": %m",`
`239`		`- blockno, fn);`
	`245`	`+ if (w < 0)`
	`246`	`+ pg_log_error("could not write block %u in file \"%s\": %m",`
	`247`	`+ blockno, fn);`
	`248`	`+ else`
	`249`	`+ pg_log_error("could not write block %u in file \"%s\": wrote %d of %d",`
	`250`	`+ blockno, fn, w, BLCKSZ);`
`240`	`251`	`exit(1);`
`241`	`252`	`}`
`242`	`253`	`}`