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[PATCH v2 06/20] fuse: Implement hole detection through lseek
From: |
Max Reitz |
Subject: |
[PATCH v2 06/20] fuse: Implement hole detection through lseek |
Date: |
Tue, 22 Sep 2020 12:49:18 +0200 |
This is a relatively new feature in libfuse (available since 3.8.0,
which was released in November 2019), so we have to let configure check
whether it is available before making use of it.
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
configure | 32 +++++++++++++++++++
block/export/fuse.c | 77 +++++++++++++++++++++++++++++++++++++++++++++
meson.build | 1 +
3 files changed, 110 insertions(+)
diff --git a/configure b/configure
index 21c31e4694..6b9184b62a 100755
--- a/configure
+++ b/configure
@@ -6226,11 +6226,39 @@ EOF
fuse_libs=$(pkg-config --libs fuse3)
if compile_prog "$fuse_cflags" "$fuse_libs"; then
fuse=yes
+
+ cat > $TMPC <<EOF
+#define FUSE_USE_VERSION 31
+#include <fuse.h>
+#include <fuse_lowlevel.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+static void fuse_lseek(fuse_req_t req, fuse_ino_t inode, off_t offset,
+ int whence, struct fuse_file_info *fi)
+{
+ if (whence == SEEK_DATA || whence == SEEK_HOLE) {
+ fuse_reply_lseek(req, offset);
+ } else {
+ fuse_reply_err(req, EINVAL);
+ }
+}
+const struct fuse_lowlevel_ops fuse_ops = {
+ .lseek = fuse_lseek,
+};
+int main(void) { return 0; }
+EOF
+ if compile_prog "$fuse_cflags" "$fuse_libs"; then
+ fuse_lseek=yes
+ else
+ fuse_lseek=no
+ fi
else
if test "$fuse" = "yes"; then
feature_not_found "fuse"
fi
fuse=no
+ fuse_lseek=no
fi
fi
@@ -7425,6 +7453,10 @@ if test "$fuse" = "yes"; then
echo "CONFIG_FUSE=y" >> $config_host_mak
echo "FUSE_CFLAGS=$fuse_cflags" >> $config_host_mak
echo "FUSE_LIBS=$fuse_libs" >> $config_host_mak
+
+ if test "$fuse_lseek" = "yes"; then
+ echo "CONFIG_FUSE_LSEEK=y" >> $config_host_mak
+ fi
fi
if test "$tcg_interpreter" = "yes"; then
diff --git a/block/export/fuse.c b/block/export/fuse.c
index 7dfb4eb280..ee90f5a185 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -548,6 +548,80 @@ static void fuse_flush(fuse_req_t req, fuse_ino_t inode,
fuse_reply_err(req, ret < 0 ? -ret : 0);
}
+#ifdef CONFIG_FUSE_LSEEK
+/**
+ * Let clients inquire allocation status.
+ */
+static void fuse_lseek(fuse_req_t req, fuse_ino_t inode, off_t offset,
+ int whence, struct fuse_file_info *fi)
+{
+ FuseExport *exp = fuse_req_userdata(req);
+
+ if (whence != SEEK_HOLE && whence != SEEK_DATA) {
+ fuse_reply_err(req, EINVAL);
+ return;
+ }
+
+ while (true) {
+ int64_t pnum;
+ int ret;
+
+ ret = bdrv_block_status_above(blk_bs(exp->common.blk), NULL,
+ offset, INT64_MAX, &pnum, NULL, NULL);
+ if (ret < 0) {
+ fuse_reply_err(req, -ret);
+ return;
+ }
+
+ if (!pnum && (ret & BDRV_BLOCK_EOF)) {
+ int64_t blk_len;
+
+ /*
+ * If blk_getlength() rounds (e.g. by sectors), then the
+ * export length will be rounded, too. However,
+ * bdrv_block_status_above() may return EOF at unaligned
+ * offsets. We must not let this become visible and thus
+ * always simulate a hole between @offset (the real EOF)
+ * and @blk_len (the client-visible EOF).
+ */
+
+ blk_len = blk_getlength(exp->common.blk);
+ if (blk_len < 0) {
+ fuse_reply_err(req, -blk_len);
+ return;
+ }
+
+ if (offset > blk_len || whence == SEEK_DATA) {
+ fuse_reply_err(req, ENXIO);
+ } else {
+ fuse_reply_lseek(req, offset);
+ }
+ return;
+ }
+
+ if (ret & BDRV_BLOCK_DATA) {
+ if (whence == SEEK_DATA) {
+ fuse_reply_lseek(req, offset);
+ return;
+ }
+ } else {
+ if (whence == SEEK_HOLE) {
+ fuse_reply_lseek(req, offset);
+ return;
+ }
+ }
+
+ /* Safety check against infinite loops */
+ if (!pnum) {
+ fuse_reply_err(req, ENXIO);
+ return;
+ }
+
+ offset += pnum;
+ }
+}
+#endif
+
static const struct fuse_lowlevel_ops fuse_ops = {
.lookup = fuse_lookup,
.getattr = fuse_getattr,
@@ -557,6 +631,9 @@ static const struct fuse_lowlevel_ops fuse_ops = {
.write = fuse_write,
.fallocate = fuse_fallocate,
.flush = fuse_flush,
+#ifdef CONFIG_FUSE_LSEEK
+ .lseek = fuse_lseek,
+#endif
};
const BlockExportDriver blk_exp_fuse = {
diff --git a/meson.build b/meson.build
index 85addd8562..1db6a46d14 100644
--- a/meson.build
+++ b/meson.build
@@ -1537,6 +1537,7 @@ summary_info += {'thread sanitizer':
config_host.has_key('CONFIG_TSAN')}
summary_info += {'rng-none': config_host.has_key('CONFIG_RNG_NONE')}
summary_info += {'Linux keyring':
config_host.has_key('CONFIG_SECRET_KEYRING')}
summary_info += {'fuse exports': config_host.has_key('CONFIG_FUSE')}
+summary_info += {'fuse lseek': config_host.has_key('CONFIG_FUSE_LSEEK')}
summary(summary_info, bool_yn: true)
if not supported_cpus.contains(cpu)
--
2.26.2
- [PATCH v2 00/20] block/export: Allow exporting BDSs via FUSE, Max Reitz, 2020/09/22
- [PATCH v2 01/20] configure: Detect libfuse, Max Reitz, 2020/09/22
- [PATCH v2 03/20] fuse: Implement standard FUSE operations, Max Reitz, 2020/09/22
- [PATCH v2 04/20] fuse: Allow growable exports, Max Reitz, 2020/09/22
- [PATCH v2 02/20] fuse: Allow exporting BDSs via FUSE, Max Reitz, 2020/09/22
- [PATCH v2 05/20] fuse: (Partially) implement fallocate(), Max Reitz, 2020/09/22
- [PATCH v2 06/20] fuse: Implement hole detection through lseek,
Max Reitz <=
- [PATCH v2 07/20] iotests: Do not needlessly filter _make_test_img, Max Reitz, 2020/09/22
- [PATCH v2 08/20] iotests: Do not pipe _make_test_img, Max Reitz, 2020/09/22
- [PATCH v2 09/20] iotests: Use convert -n in some cases, Max Reitz, 2020/09/22
- [PATCH v2 10/20] iotests/046: Avoid renaming images, Max Reitz, 2020/09/22
- [PATCH v2 11/20] iotests: Derive image names from $TEST_IMG, Max Reitz, 2020/09/22
- [PATCH v2 12/20] iotests/091: Use _cleanup_qemu instad of "wait", Max Reitz, 2020/09/22
- [PATCH v2 13/20] iotests: Restrict some Python tests to file, Max Reitz, 2020/09/22
- [PATCH v2 15/20] iotests/287: Clean up subshell test image, Max Reitz, 2020/09/22
- [PATCH v2 16/20] storage-daemon: Call bdrv_close_all() on exit, Max Reitz, 2020/09/22
- [PATCH v2 14/20] iotests: Let _make_test_img guess $TEST_IMG_FILE, Max Reitz, 2020/09/22