From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
In unix_zeroout() for files, we should try a ZERO_RANGE before we try
PUNCH_HOLE because the former will not cause us to lose preallocated
blocks. Since block devices have supported fallocate for a few years
now, refactor the fallocate calls into a helper and call it from either
case.
Reported-by: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
---
lib/ext2fs/unix_io.c | 53 ++++++++++++++++++++++++++++----------------------
1 file changed, 30 insertions(+), 23 deletions(-)
diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index 7a4c9bf5e..74fc8a75d 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -1126,6 +1126,31 @@ static errcode_t unix_discard(io_channel channel, unsigned long long block,
return EXT2_ET_UNIMPLEMENTED;
}
+/*
+ * If we know about ZERO_RANGE, try that before we try PUNCH_HOLE because
+ * ZERO_RANGE doesn't unmap preallocated blocks. We prefer fallocate because
+ * it always invalidates page cache, and libext2fs requires that reads after
+ * ZERO_RANGE return zeroes.
+ */
+static int __unix_zeroout(int fd, off_t offset, off_t len)
+{
+ int ret = -1;
+
+#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_ZERO_RANGE)
+ ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, offset, len);
+ if (ret == 0)
+ return 0;
+#endif
+#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)
+ ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+ offset, len);
+ if (ret == 0)
+ return 0;
+#endif
+ errno = EOPNOTSUPP;
+ return ret;
+}
+
/* parameters might not be used if OS doesn't support zeroout */
#if __GNUC_PREREQ (4, 6)
#pragma GCC diagnostic push
@@ -1144,10 +1169,7 @@ static errcode_t unix_zeroout(io_channel channel, unsigned long long block,
if (safe_getenv("UNIX_IO_NOZEROOUT"))
goto unimplemented;
- if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
- /* Not implemented until the BLKZEROOUT mess is fixed */
- goto unimplemented;
- } else {
+ if (!(channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE)) {
/* Regular file, try to use truncate/punch/zero. */
struct stat statbuf;
@@ -1167,26 +1189,11 @@ static errcode_t unix_zeroout(io_channel channel, unsigned long long block,
if (ret)
goto err;
}
-#if defined(HAVE_FALLOCATE) && (defined(FALLOC_FL_ZERO_RANGE) || \
- (defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)))
-#if defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)
- ret = fallocate(data->dev,
- FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
- (off_t)(block) * channel->block_size + data->offset,
- (off_t)(count) * channel->block_size);
- if (ret == 0)
- goto err;
-#endif
-#ifdef FALLOC_FL_ZERO_RANGE
- ret = fallocate(data->dev,
- FALLOC_FL_ZERO_RANGE,
- (off_t)(block) * channel->block_size + data->offset,
- (off_t)(count) * channel->block_size);
-#endif
-#else
- goto unimplemented;
-#endif /* HAVE_FALLOCATE && (ZERO_RANGE || (PUNCH_HOLE && KEEP_SIZE)) */
}
+
+ ret = __unix_zeroout(data->dev,
+ (off_t)(block) * channel->block_size + data->offset,
+ (off_t)(count) * channel->block_size);
err:
if (ret < 0) {
if (errno == EOPNOTSUPP)
