From 156d7a1e123f85863db854aae5c10acd3864f9d8 Mon Sep 17 00:00:00 2001

From: Peter Jones <pjones@redhat.com>

Date: Fri, 11 Oct 2019 14:20:54 -0400

Subject: [PATCH 56/63] Try even harder to find disk device symlinks in sysfs.

Today's realization is that the thing encoded into the structure of

sysfs is, in the best case, the dependency graph of the makefile targets

to build a device driver.

In the case of nvme-fabric, or really wherever the kernel has

class_create() and device_create() in the same function, there's an

extra level of indirection.

Anyway, in this patch we stop pretending sysfs isn't completely absurd,

and just try adding "/device" in the middle of the driver symlink path,

until we actually either get ENOENT on the device symlink or find a

device symlink that actually has a driver symlink under it.

Signed-off-by: Peter Jones <pjones@redhat.com>

---

 src/linux-nvme.c | 13 +++++----

 src/linux.c      | 46 ++++++++++++++++++--------------

 src/linux.h      | 69 ++++++++++++++++++++++++++++++++++++++++++++++++

 3 files changed, 101 insertions(+), 27 deletions(-)

diff --git a/src/linux-nvme.c b/src/linux-nvme.c

index 7b18d7990ac..455c4c7ba9b 100644

--- a/src/linux-nvme.c

+++ b/src/linux-nvme.c

@@ -87,13 +87,12 @@ parse_nvme(struct device *dev, const char *current, const char *root UNUSED)

 	/*

 	 * now fish the eui out of sysfs is there is one...

 	 */

-	rc = read_sysfs_file(&filebuf,

-	                     "class/block/nvme%dn%d/eui",

-	                     ctrl_id, ns_id);

-	if ((rc < 0 && errno == ENOENT) || filebuf == NULL) {

-	        rc = read_sysfs_file(&filebuf,

-	                     "class/block/nvme%dn%d/device/eui",

-	                     ctrl_id, ns_id);

+	char *euipath = NULL;

+	rc = read_sysfs_file(&filebuf, "class/block/nvme%dn%d/eui", ctrl_id, ns_id);

+	if (rc < 0 && (errno == ENOENT || errno == ENOTDIR)) {

+		rc = find_device_file(&euipath, "eui", "class/block/nvme%dn%d", ctrl_id, ns_id);

+		if (rc >= 0 && euipath != NULL)

+			rc = read_sysfs_file(&filebuf, "%s", euipath);

 	}

 	if (rc >= 0 && filebuf != NULL) {

 	        uint8_t eui[8];

diff --git a/src/linux.c b/src/linux.c

index 73c67cbafd3..30db22d95dd 100644

--- a/src/linux.c

+++ b/src/linux.c

@@ -401,26 +401,32 @@ struct device HIDDEN

 	        goto err;

 	}

-	if (dev->device[0] != 0) {

-	        rc = sysfs_readlink(&tmpbuf, "block/%s/device/driver", dev->disk_name);

+	/*

+	 * So, on a normal disk, you get something like:

+	 * /sys/block/sda/device -> ../../0:0:0:0

+	 * /sys/block/sda/device/driver -> ../../../../../../../bus/scsi/drivers/sd

+	 *

+	 * On a directly attached nvme device you get:

+	 * /sys/block/nvme0n1/device -> ../../nvme0

+	 * /sys/block/nvme0n1/device/device -> ../../../0000:6e:00.0

+	 * /sys/block/nvme0n1/device/device/driver -> ../../../../bus/pci/drivers/nvme

+	 *

+	 * On a fabric-attached nvme device, you get something like:

+	 * /sys/block/nvme0n1/device -> ../../nvme0

+	 * /sys/block/nvme0n1/device/device -> ../../ctl

+	 * /sys/block/nvme0n1/device/device/device -> ../../../../../0000:6e:00.0

+	 * /sys/block/nvme0n1/device/device/device/driver -> ../../../../../../bus/pci/drivers/nvme-fabrics

+	 *

+	 * ... I think?  I don't have one in front of me.

+	 */

+

+	char *filepath = NULL;

+	rc = find_device_file(&filepath, "driver", "block/%s", dev->disk_name);

+	if (rc >= 0) {

+		rc = sysfs_readlink(&tmpbuf, "%s", filepath);

 	        if (rc < 0 || !tmpbuf) {

-	                if (errno == ENOENT) {

-	                        /*

-	                         * nvme, for example, will have nvme0n1/device point

-	                         * at nvme0, and we need to look for device/driver

-	                         * there.

-	                         */

-	                        rc = sysfs_readlink(&tmpbuf,

-	                                            "block/%s/device/device/driver",

-	                                            dev->disk_name);

-	                        if (rc >= 0 && tmpbuf)

-	                                efi_error_pop();

-	                }

-	                if (rc < 0 || !tmpbuf) {

-	                        efi_error("readlink of /sys/block/%s/device/driver failed",

-	                                  dev->disk_name);

-	                        goto err;

-	                }

+			efi_error("readlink of /sys/%s failed", filepath);

+	                goto err;

 	        }

 	        linkbuf = pathseg(tmpbuf, -1);

@@ -431,7 +437,7 @@ struct device HIDDEN

 	        dev->driver = strdup(linkbuf);

 	} else {

-	        dev->driver = strdup("");

+		dev->driver = strdup("");

 	}

 	if (!dev->driver) {

diff --git a/src/linux.h b/src/linux.h

index 5ae64ffaacf..ae9835ef7ce 100644

--- a/src/linux.h

+++ b/src/linux.h

@@ -218,6 +218,22 @@ extern ssize_t HIDDEN make_mac_path(uint8_t *buf, ssize_t size,

 		_rc;							\

 	})

+#define sysfs_access(mode, fmt, args...)				\

+	({								\

+		int rc_;						\

+		char *pn_;						\

+									\

+		rc_ = asprintfa(&pn_, "/sys/" fmt, ## args);		\

+		if (rc_ >= 0) {						\

+			rc_ = access(pn_, mode);			\

+			if (rc_ < 0)					\

+				efi_error("could not access %s", pn_);  \

+		} else {						\

+			efi_error("could not allocate memory");		\

+		}							\

+		rc_;							\

+	})

+

 #define sysfs_stat(statbuf, fmt, args...)				\

 	({								\

 		int rc_;						\

@@ -251,6 +267,59 @@ extern ssize_t HIDDEN make_mac_path(uint8_t *buf, ssize_t size,

 		dir_;							\

 	})

+/*

+ * Iterate a /sys/block directory looking for device/foo, device/device/foo,

+ * etc.  I'm not proud of this method.

+ */

+#define find_device_file(result, name, fmt, args...)				\

+	({									\

+		int rc_ = 0;							\

+		debug("searching for %s from in %s", name, dev->disk_name);	\

+		for (unsigned int try_ = 0; true; try_++) {			\

+			char slashdev_[sizeof("device")				\

+				       + try_ * strlen("/device")];		\

+										\

+			char *nul_ = stpcpy(slashdev_, "device");		\

+			for (unsigned int i_ = 0; i_ < try_; i_++)		\

+				nul_ = stpcpy(nul_, "/device");			\

+										\

+			debug("trying /sys/" fmt "/%s/%s",			\

+			      ## args, slashdev_, name);			\

+										\

+			rc_ = sysfs_access(F_OK, fmt "/%s", ## args, slashdev_);\

+			if (rc_ < 0) {						\

+				if (errno == ENOENT) {				\

+					efi_error_pop();			\

+					break;					\

+				}						\

+				efi_error("cannot access /sys/"fmt"/%s: %m",	\

+					  ## args, slashdev_);			\

+				goto find_device_link_err_;			\

+			}							\

+										\

+			rc_ = sysfs_access(F_OK, fmt "/%s/%s",			\

+					   ## args, slashdev_, name);		\

+			if (rc_ < 0) {						\

+				if (errno == ENOENT) {				\

+					efi_error_pop();			\

+					break;					\

+				}						\

+				efi_error("cannot access /sys/"fmt"/%s/%s: %m",	\

+					  ## args, slashdev_, name);		\

+				goto find_device_link_err_;			\

+			}							\

+										\

+			rc_ = asprintfa(result, fmt "/%s/%s",			\

+					## args, slashdev_, name);		\

+			if (rc_ < 0) {						\

+				efi_error("cannot allocate memory: %m");	\

+				goto find_device_link_err_;			\

+			}							\

+		}								\

+find_device_link_err_:								\

+		rc_;								\

+	})

+

 #define DEV_PROVIDES_ROOT       1

 #define DEV_PROVIDES_HD	 2

 #define DEV_ABBREV_ONLY	 4

-- 

2.26.2