From: Karel Zak <kzak@redhat.com>
Date: Wed, 29 Jul 2026 10:12:27 +0000 (+0200)
Subject: libfdisk: add pluggable VFS I/O support
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7eaac640e2339b318967fc47df94b35f24991170;p=thirdparty%2Futil-linux.git

libfdisk: add pluggable VFS I/O support

Add fdisk_set_vfs() to allow replacing standard I/O syscalls
(read/write/lseek/open/close/fsync) with custom implementations,
matching the existing VFS support in libblkid and libmount.

All direct I/O calls in the library (context.c, utils.c, dos.c,
gpt.c, bsd.c, sgi.c, sun.c) are replaced with ul_vfs_* wrappers
that fall back to standard syscalls when no VFS is set.

The VFS is also propagated to libblkid probes used in wipe.c
for collision detection and signature wiping.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libfdisk/docs/libfdisk-sections.txt b/libfdisk/docs/libfdisk-sections.txt
index 53fa1a179..872231628 100644
--- a/libfdisk/docs/libfdisk-sections.txt
+++ b/libfdisk/docs/libfdisk-sections.txt
@@ -356,6 +356,7 @@ fdisk_set_first_lba
 fdisk_set_last_lba
 fdisk_set_size_unit
 fdisk_set_unit
+fdisk_set_vfs
 FDISK_SINGULAR
 fdisk_unref_context
 fdisk_use_cylinders
diff --git a/libfdisk/src/bsd.c b/libfdisk/src/bsd.c
index 6ecbdef60..92931e95f 100644
--- a/libfdisk/src/bsd.c
+++ b/libfdisk/src/bsd.c
@@ -638,19 +638,19 @@ static int bsd_get_bootstrap(struct fdisk_context *cxt,
 {
 	int fd;
 
-	if ((fd = open(path, O_RDONLY)) < 0) {
+	if ((fd = ul_vfs_open(cxt->vfs, path, O_RDONLY, 0)) < 0) {
 		fdisk_warn(cxt, _("cannot open %s"), path);
 		return -errno;
 	}
 
-	if (ul_read_all(fd, ptr, size) != size) {
+	if (ul_vfs_read_all(cxt->vfs, fd, ptr, size) != size) {
 		fdisk_warn(cxt, _("cannot read %s"), path);
-		close(fd);
+		ul_vfs_close(cxt->vfs, fd);
 		return -errno;
 	}
 
 	fdisk_info(cxt, _("The bootstrap file %s successfully loaded."), path);
-	close (fd);
+	ul_vfs_close(cxt->vfs, fd);
 	return 0;
 }
 
@@ -715,12 +715,12 @@ int fdisk_bsd_write_bootstrap(struct fdisk_context *cxt)
 #if defined (__alpha__)
 	alpha_bootblock_checksum(l->bsdbuffer);
 #endif
-	if (lseek(cxt->dev_fd, (off_t) sector * DEFAULT_SECTOR_SIZE, SEEK_SET) == -1) {
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, (off_t) sector * DEFAULT_SECTOR_SIZE, SEEK_SET) == -1) {
 		fdisk_warn(cxt, _("seek on %s failed"), cxt->dev_path);
 		rc = -errno;
 		goto done;
 	}
-	if (ul_write_all(cxt->dev_fd, l->bsdbuffer, BSD_BBSIZE)) {
+	if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, l->bsdbuffer, BSD_BBSIZE)) {
 		fdisk_warn(cxt, _("cannot write %s"), cxt->dev_path);
 		rc = -errno;
 		goto done;
@@ -837,9 +837,9 @@ static int bsd_readlabel(struct fdisk_context *cxt)
 		 * partition. Note that DOS uses native sector size. */
 		offset = dos_partition_get_start(l->dos_part) * cxt->sector_size;
 
-	if (lseek(cxt->dev_fd, offset, SEEK_SET) == -1)
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET) == -1)
 		return -1;
-	if (ul_read_all(cxt->dev_fd, l->bsdbuffer, sizeof(l->bsdbuffer)) < 0)
+	if (ul_vfs_read_all(cxt->vfs, cxt->dev_fd, l->bsdbuffer, sizeof(l->bsdbuffer)) < 0)
 		return errno ? -errno : -1;
 
 	/* The offset to begin of the disk label. Note that BSD uses
@@ -899,11 +899,11 @@ static int bsd_write_disklabel(struct fdisk_context *cxt)
 	/* Write the checksum to the end of the first sector. */
 	alpha_bootblock_checksum(l->bsdbuffer);
 #endif
-	if (lseek(cxt->dev_fd, offset, SEEK_SET) == -1) {
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET) == -1) {
 		fdisk_warn(cxt, _("seek on %s failed"), cxt->dev_path);
 		return -errno;
 	}
-	if (ul_write_all(cxt->dev_fd, l->bsdbuffer, sizeof(l->bsdbuffer))) {
+	if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, l->bsdbuffer, sizeof(l->bsdbuffer))) {
 		fdisk_warn(cxt, _("cannot write %s"), cxt->dev_path);
 		return -errno;
 	}
diff --git a/libfdisk/src/context.c b/libfdisk/src/context.c
index 0c5cf52bc..2c407029e 100644
--- a/libfdisk/src/context.c
+++ b/libfdisk/src/context.c
@@ -110,6 +110,7 @@ static int init_nested_from_parent(struct fdisk_context *cxt, int isnew)
 	cxt->user_geom =	parent->user_geom;
 	cxt->user_log_sector =	parent->user_log_sector;
 	cxt->user_pyh_sector =  parent->user_pyh_sector;
+	cxt->vfs =		parent->vfs;
 
 	/* parent <--> nested independent setting, initialize for new nested
 	 * contexts only */
@@ -347,6 +348,47 @@ int fdisk_enable_bootbits_protection(struct fdisk_context *cxt, int enable)
 	cxt->protect_bootbits = enable ? 1 : 0;
 	return 0;
 }
+
+/**
+ * fdisk_set_vfs:
+ * @cxt: fdisk context
+ * @ops: VFS operations or NULL to reset to defaults
+ *
+ * Sets custom I/O operations for the context. This allows replacing
+ * standard read/write/lseek/etc. with custom implementations
+ * (e.g., fiber-aware I/O).
+ *
+ * The @ops struct is copied into a private allocation owned by the
+ * context. The caller sets ops->size to sizeof(struct ul_vfs_ops) to
+ * enable forward/backward compatibility. NULL function pointers fall
+ * back to standard syscalls. Passing @ops as NULL frees the private
+ * copy and resets the context to default (direct syscall) I/O.
+ *
+ * Note: fdisk_set_vfs() should be called before fdisk_assign_device().
+ *
+ * Since: 2.43
+ *
+ * Returns: 0 on success, or <0 in case of error.
+ */
+int fdisk_set_vfs(struct fdisk_context *cxt, const struct ul_vfs_ops *ops)
+{
+	if (!cxt)
+		return -EINVAL;
+
+	if (!ops) {
+		free(cxt->vfs);
+		cxt->vfs = NULL;
+		return 0;
+	}
+	if (!cxt->vfs) {
+		cxt->vfs = calloc(1, sizeof(*cxt->vfs));
+		if (!cxt->vfs)
+			return -ENOMEM;
+	}
+	ul_vfs_init(cxt->vfs, ops);
+	return 0;
+}
+
 /**
  * fdisk_disable_dialogs
  * @cxt: fdisk context
@@ -560,9 +602,11 @@ static void reset_context(struct fdisk_context *cxt)
 	} else {
 		/* we close device only in primary context */
 		if (cxt->dev_fd > -1 && cxt->is_priv)
-			close(cxt->dev_fd);
+			ul_vfs_close(cxt->vfs, cxt->dev_fd);
 		DBG_OBJ(CXT, cxt, ul_debug("  freeing firstsector"));
 		free(cxt->firstsector);
+		free(cxt->vfs);
+		cxt->vfs = NULL;
 	}
 
 	free(cxt->dev_path);
@@ -715,11 +759,11 @@ int fdisk_assign_device(struct fdisk_context *cxt,
 		flags |= (O_RDWR | O_EXCL);
 
 	errno = 0;
-	fd = open(fname,flags);
+	fd = ul_vfs_open(cxt->vfs, fname, flags, 0);
 	if (fd < 0 && errno == EBUSY && (flags & O_EXCL)) {
 		flags &= ~O_EXCL;
 		errno = 0;
-		fd = open(fname, flags);
+		fd = ul_vfs_open(cxt->vfs, fname, flags, 0);
 	}
 
 	if (fd < 0) {
@@ -730,7 +774,7 @@ int fdisk_assign_device(struct fdisk_context *cxt,
 
 	rc = fdisk_assign_fd(cxt, fd, fname, readonly, 1, flags & O_EXCL);
 	if (rc)
-		close(fd);
+		ul_vfs_close(cxt->vfs, fd);
 	return rc;
 }
 
@@ -784,14 +828,14 @@ int fdisk_deassign_device(struct fdisk_context *cxt, int nosync)
 	DBG_OBJ(CXT, cxt, ul_debug("de-assigning device %s", cxt->dev_path));
 
 	if (cxt->readonly && cxt->is_priv)
-		close(cxt->dev_fd);
+		ul_vfs_close(cxt->vfs, cxt->dev_fd);
 	else {
-		if (fsync(cxt->dev_fd)) {
+		if (ul_vfs_fsync(cxt->vfs, cxt->dev_fd)) {
 			fdisk_warn(cxt, _("%s: fsync device failed"),
 					cxt->dev_path);
 			return -errno;
 		}
-		if (cxt->is_priv && close(cxt->dev_fd)) {
+		if (cxt->is_priv && ul_vfs_close(cxt->vfs, cxt->dev_fd)) {
 			fdisk_warn(cxt, _("%s: close device failed"),
 					cxt->dev_path);
 			return -errno;
diff --git a/libfdisk/src/dos.c b/libfdisk/src/dos.c
index 1731c1ef1..68fd4e050 100644
--- a/libfdisk/src/dos.c
+++ b/libfdisk/src/dos.c
@@ -229,7 +229,7 @@ static int seek_sector(struct fdisk_context *cxt, fdisk_sector_t secno)
 {
 	off_t offset = (off_t) secno * cxt->sector_size;
 
-	return lseek(cxt->dev_fd, offset, SEEK_SET) == (off_t) -1 ? -errno : 0;
+	return ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET) == (off_t) -1 ? -errno : 0;
 }
 
 static int read_sector(struct fdisk_context *cxt, fdisk_sector_t secno,
@@ -241,7 +241,7 @@ static int read_sector(struct fdisk_context *cxt, fdisk_sector_t secno,
 	if (rc < 0)
 		return rc;
 
-	r = read(cxt->dev_fd, buf, cxt->sector_size);
+	r = ul_vfs_read(cxt->vfs, cxt->dev_fd, buf, cxt->sector_size);
 	if (r == (ssize_t) cxt->sector_size)
 		return 0;
 	if (r < 0)
@@ -2126,7 +2126,7 @@ static int write_sector(struct fdisk_context *cxt, fdisk_sector_t secno,
 
 	DBG(LABEL, ul_debug("DOS: writing to sector %ju", (uintmax_t) secno));
 
-	if (write(cxt->dev_fd, buf, cxt->sector_size) != (ssize_t) cxt->sector_size)
+	if (ul_vfs_write(cxt->vfs, cxt->dev_fd, buf, cxt->sector_size) != (ssize_t) cxt->sector_size)
 		return -errno;
 	return 0;
 }
diff --git a/libfdisk/src/fdiskP.h b/libfdisk/src/fdiskP.h
index d9a9d9666..446f3962f 100644
--- a/libfdisk/src/fdiskP.h
+++ b/libfdisk/src/fdiskP.h
@@ -21,6 +21,7 @@
 
 #include "c.h"
 #include "libfdisk.h"
+#include "vfs.h"
 
 #include "list.h"
 #include "debug.h"
@@ -438,6 +439,8 @@ struct fdisk_context {
 
 	struct fdisk_context	*parent;	/* for nested PT */
 	struct fdisk_script	*script;	/* what we want to follow */
+
+	struct ul_vfs_ops	*vfs;		/* pluggable I/O ops (owned, or NULL) */
 };
 
 /* table */
diff --git a/libfdisk/src/gpt.c b/libfdisk/src/gpt.c
index cf4f77808..b8db94d34 100644
--- a/libfdisk/src/gpt.c
+++ b/libfdisk/src/gpt.c
@@ -999,9 +999,9 @@ static ssize_t read_lba(struct fdisk_context *cxt, uint64_t lba,
 {
 	off_t offset = lba * cxt->sector_size;
 
-	if (lseek(cxt->dev_fd, offset, SEEK_SET) == (off_t) -1)
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET) == (off_t) -1)
 		return -1;
-	return (size_t)read(cxt->dev_fd, buffer, bytes) != bytes;
+	return (size_t)ul_vfs_read(cxt->vfs, cxt->dev_fd, buffer, bytes) != bytes;
 }
 
 
@@ -1033,10 +1033,10 @@ static unsigned char *gpt_read_entries(struct fdisk_context *cxt,
 	offset = (off_t) le64_to_cpu(header->partition_entry_lba) *
 		       cxt->sector_size;
 
-	if (offset != lseek(cxt->dev_fd, offset, SEEK_SET))
+	if (offset != ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET))
 		goto fail;
 
-	ssz = read(cxt->dev_fd, ret, sz);
+	ssz = ul_vfs_read(cxt->vfs, cxt->dev_fd, ret, sz);
 	if (ssz < 0 || (size_t) ssz != sz)
 		goto fail;
 
@@ -2064,10 +2064,10 @@ static int gpt_set_partition(struct fdisk_context *cxt, size_t n,
 
 static int gpt_read(struct fdisk_context *cxt, off_t offset, void *buf, size_t count)
 {
-	if (offset != lseek(cxt->dev_fd, offset, SEEK_SET))
+	if (offset != ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET))
 		return -errno;
 
-	if (ul_read_all(cxt->dev_fd, buf, count))
+	if (ul_vfs_read_all(cxt->vfs, cxt->dev_fd, buf, count))
 		return -errno;
 
 	DBG(GPT, ul_debug("  read OK [offset=%zu, size=%zu]",
@@ -2077,13 +2077,13 @@ static int gpt_read(struct fdisk_context *cxt, off_t offset, void *buf, size_t c
 
 static int gpt_write(struct fdisk_context *cxt, off_t offset, void *buf, size_t count)
 {
-	if (offset != lseek(cxt->dev_fd, offset, SEEK_SET))
+	if (offset != ul_vfs_lseek(cxt->vfs, cxt->dev_fd, offset, SEEK_SET))
 		return -errno;
 
-	if (ul_write_all(cxt->dev_fd, buf, count))
+	if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, buf, count))
 		return -errno;
 
-	if (fsync(cxt->dev_fd) != 0)
+	if (ul_vfs_fsync(cxt->vfs, cxt->dev_fd) != 0)
 		return -errno;
 
 	DBG(GPT, ul_debug("  write OK [offset=%zu, size=%zu]",
diff --git a/libfdisk/src/libfdisk.h.in b/libfdisk/src/libfdisk.h.in
index c23ad475c..0aa8f9533 100644
--- a/libfdisk/src/libfdisk.h.in
+++ b/libfdisk/src/libfdisk.h.in
@@ -240,6 +240,25 @@ int fdisk_get_devfd(struct fdisk_context *cxt);
 dev_t fdisk_get_devno(struct fdisk_context *cxt);
 const char *fdisk_get_devmodel(struct fdisk_context *cxt);
 
+#ifndef UL_VFS_OPS_DEFINED
+#define UL_VFS_OPS_DEFINED
+
+struct ul_vfs_ops {
+	size_t size;
+
+	ssize_t (*vfs_read)(int fd, void *buf, size_t count);
+	ssize_t (*vfs_write)(int fd, const void *buf, size_t count);
+	int     (*vfs_open)(const char *pathname, int flags, mode_t mode);
+	int     (*vfs_close)(int fd);
+	off_t   (*vfs_lseek)(int fd, off_t offset, int whence);
+	int     (*vfs_fsync)(int fd);
+
+	FILE   *(*vfs_fopen)(const char *pathname, const char *mode);
+};
+
+#endif /* UL_VFS_OPS_DEFINED */
+
+extern int fdisk_set_vfs(struct fdisk_context *cxt, const struct ul_vfs_ops *ops);
 
 unsigned int fdisk_get_geom_heads(struct fdisk_context *cxt);
 fdisk_sector_t fdisk_get_geom_sectors(struct fdisk_context *cxt);
diff --git a/libfdisk/src/libfdisk.sym b/libfdisk/src/libfdisk.sym
index eaeea0988..6f02bcf77 100644
--- a/libfdisk/src/libfdisk.sym
+++ b/libfdisk/src/libfdisk.sym
@@ -337,4 +337,5 @@ FDISK_2_43 {
 	fdisk_script_disable_devnames;
 	fdisk_script_has_devnames;
 	fdisk_get_recommended_labelname;
+	fdisk_set_vfs;
 } FDISK_2_42;
diff --git a/libfdisk/src/sgi.c b/libfdisk/src/sgi.c
index 1ec14f0e0..a5dfd9bdf 100644
--- a/libfdisk/src/sgi.c
+++ b/libfdisk/src/sgi.c
@@ -482,9 +482,9 @@ static int sgi_write_disklabel(struct fdisk_context *cxt)
 
 	assert(sgi_pt_checksum(sgilabel) == 0);
 
-	if (lseek(cxt->dev_fd, 0, SEEK_SET) < 0)
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, 0, SEEK_SET) < 0)
 		goto err;
-	if (ul_write_all(cxt->dev_fd, sgilabel, DEFAULT_SECTOR_SIZE))
+	if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, sgilabel, DEFAULT_SECTOR_SIZE))
 		goto err;
 	if (!strncmp((char *) sgilabel->volume[0].name, "sgilabel", 8)) {
 		/*
@@ -494,13 +494,13 @@ static int sgi_write_disklabel(struct fdisk_context *cxt)
 		int infostartblock
 			= be32_to_cpu(sgilabel->volume[0].block_num);
 
-		if (lseek(cxt->dev_fd, (off_t) infostartblock *
+		if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, (off_t) infostartblock *
 					DEFAULT_SECTOR_SIZE, SEEK_SET) < 0)
 			goto err;
 		info = sgi_new_info();
 		if (!info)
 			goto err;
-		if (ul_write_all(cxt->dev_fd, info, sizeof(*info)))
+		if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, info, sizeof(*info)))
 			goto err;
 	}
 
diff --git a/libfdisk/src/sun.c b/libfdisk/src/sun.c
index 2328b03ec..d72deba22 100644
--- a/libfdisk/src/sun.c
+++ b/libfdisk/src/sun.c
@@ -1024,9 +1024,9 @@ static int sun_write_disklabel(struct fdisk_context *cxt)
 	sunlabel->csum = 0;
 	sunlabel->csum = sun_pt_checksum(sunlabel);
 
-	if (lseek(cxt->dev_fd, 0, SEEK_SET) < 0)
+	if (ul_vfs_lseek(cxt->vfs, cxt->dev_fd, 0, SEEK_SET) < 0)
 		return -errno;
-	if (ul_write_all(cxt->dev_fd, sunlabel, sz) != 0)
+	if (ul_vfs_write_all(cxt->vfs, cxt->dev_fd, sunlabel, sz) != 0)
 		return -errno;
 
 	return 0;
diff --git a/libfdisk/src/utils.c b/libfdisk/src/utils.c
index 58b2d9bae..805c40abe 100644
--- a/libfdisk/src/utils.c
+++ b/libfdisk/src/utils.c
@@ -22,7 +22,7 @@ static int read_from_device(struct fdisk_context *cxt,
 	DBG_OBJ(CXT, cxt, ul_debug("reading: offset=%ju, size=%zu",
 				start, size));
 
-	r = lseek(cxt->dev_fd, start, SEEK_SET);
+	r = ul_vfs_lseek(cxt->vfs, cxt->dev_fd, start, SEEK_SET);
 	if (r == -1)
 	{
 		DBG_OBJ(CXT, cxt, ul_debug("failed to seek to offset %ju: %m", start));
@@ -30,7 +30,7 @@ static int read_from_device(struct fdisk_context *cxt,
 	}
 
 	errno = 0;
-	r = read(cxt->dev_fd, buf, size);
+	r = ul_vfs_read(cxt->vfs, cxt->dev_fd, buf, size);
 	if (r < 0 || (size_t)r != size) {
 		if (!errno)
 			errno = EINVAL;	/* probably too small file/device */
diff --git a/libfdisk/src/wipe.c b/libfdisk/src/wipe.c
index 64b8a3a96..af7ee34b3 100644
--- a/libfdisk/src/wipe.c
+++ b/libfdisk/src/wipe.c
@@ -120,6 +120,9 @@ int fdisk_do_wipe(struct fdisk_context *cxt)
 	if (!pr)
 		return -ENOMEM;
 
+	if (cxt->vfs)
+		blkid_probe_set_vfs(pr, cxt->vfs);
+
 	list_for_each(p, &cxt->wipes) {
 		struct fdisk_wipe *wp = list_entry(p, struct fdisk_wipe, wipes);
 		blkid_loff_t start = (blkid_loff_t) wp->start * cxt->sector_size,
@@ -169,6 +172,10 @@ int fdisk_check_collisions(struct fdisk_context *cxt)
 	pr = blkid_new_probe();
 	if (!pr)
 		return -ENOMEM;
+
+	if (cxt->vfs)
+		blkid_probe_set_vfs(pr, cxt->vfs);
+
 	rc = blkid_probe_set_device(pr, cxt->dev_fd, 0, 0);
 	if (rc)
 		return rc;