[PATCH 1/2] loopdev: Properly translate errors from ul_path_read_*()

[PATCH 1/2] loopdev: Properly translate errors from ul_path_read_*()

[Jan Kara]

A few callsites do not translate error from ul_path_read_*() and just
treat it as error code leading to confusing EPERM errors.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 lib/loopdev.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/loopdev.c b/lib/loopdev.c
index b5da1516e37f..27ab06c66848 100644
--- a/lib/loopdev.c
+++ b/lib/loopdev.c
@@ -739,7 +739,8 @@ int loopcxt_get_offset(struct loopdev_cxt *lc, uint64_t *offset)
 	int rc = -EINVAL;
 
 	if (sysfs)
-		rc = ul_path_read_u64(sysfs, offset, "loop/offset");
+		if (ul_path_read_u64(sysfs, offset, "loop/offset") == 0)
+			rc = 0;
 
 	if (rc && loopcxt_ioctl_enabled(lc)) {
 		struct loop_info64 *lo = loopcxt_get_info(lc);
@@ -767,7 +768,8 @@ int loopcxt_get_blocksize(struct loopdev_cxt *lc, uint64_t *blocksize)
 	int rc = -EINVAL;
 
 	if (sysfs)
-		rc = ul_path_read_u64(sysfs, blocksize, "queue/logical_block_size");
+		if (ul_path_read_u64(sysfs, blocksize, "queue/logical_block_size") == 0)
+			rc = 0;
 
 	/* Fallback based on BLKSSZGET ioctl */
 	if (rc) {
@@ -799,7 +801,8 @@ int loopcxt_get_sizelimit(struct loopdev_cxt *lc, uint64_t *size)
 	int rc = -EINVAL;
 
 	if (sysfs)
-		rc = ul_path_read_u64(sysfs, size, "loop/sizelimit");
+		if (ul_path_read_u64(sysfs, size, "loop/sizelimit") == 0)
+			rc = 0;
 
 	if (rc && loopcxt_ioctl_enabled(lc)) {
 		struct loop_info64 *lo = loopcxt_get_info(lc);
-- 
2.31.1

[PATCH 2/2] loopdev: Do not treat errors when detecting overlap as fatal

[Jan Kara]

When looking for overlapping loop device we can fail getting some loop
device properties when we race with device autoclear. Just squelsh these
errors and try next loop device.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 lib/loopdev.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/loopdev.c b/lib/loopdev.c
index 27ab06c66848..d49738fde122 100644
--- a/lib/loopdev.c
+++ b/lib/loopdev.c
@@ -1777,10 +1777,13 @@ int loopcxt_find_overlap(struct loopdev_cxt *lc, const char *filename,
 
 		rc = loopcxt_is_used(lc, hasst ? &st : NULL,
 				     filename, offset, sizelimit, 0);
-		if (!rc)
-			continue;	/* unused */
-		if (rc < 0)
-			break;		/* error */
+		/*
+		 * Either the loopdev is unused or we've got an error which can
+		 * happen when we are racing with device autoclear. Just ignore
+		 * this loopdev...
+		 */
+		if (rc <= 0)
+			continue;
 
 		DBG(CXT, ul_debugobj(lc, "found %s backed by %s",
 			loopcxt_get_device(lc), filename));
@@ -1789,13 +1792,13 @@ int loopcxt_find_overlap(struct loopdev_cxt *lc, const char *filename,
 		if (rc) {
 			DBG(CXT, ul_debugobj(lc, "failed to get offset for device %s",
 				loopcxt_get_device(lc)));
-			break;
+			continue;
 		}
 		rc = loopcxt_get_sizelimit(lc, &lc_sizelimit);
 		if (rc) {
 			DBG(CXT, ul_debugobj(lc, "failed to get sizelimit for device %s",
 				loopcxt_get_device(lc)));
-			break;
+			continue;
 		}
 
 		/* full match */
-- 
2.31.1

Re: [PATCH 1/2] loopdev: Properly translate errors from ul_path_read_*()

[Karel Zak]

On Thu, Jan 20, 2022 at 01:16:38PM +0100, Jan Kara wrote:
>  lib/loopdev.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)

 Applied (both patches), thanks!

  Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com