Bug 488283

Summary:	Thumbnails are not saved to the cache when .cache is a btrfs subvolume
Product:	[Applications] dolphin	Reporter:	ipha <ipha00>
Component:	general	Assignee:	Dolphin Bug Assignee <dolphin-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	andy, dolphin-bugs-null, kdedev, kodyvonbargen
Priority:	NOR
Version First Reported In:	24.05.2
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=489762
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description ipha 2024-06-10 01:10:30 UTC

SUMMARY
Dolphin is not saving thumbnails to the cache and instead regenerates them every time a folder is opened.
It will however still use cached thumbnails if they're available(ie, generated with gwenview)

STEPS TO REPRODUCE
1.  Clear ~/.cache/thumbnails
2.  Browse a folder with pictures, let thumbnails generate
3.  Check ~/.cache/thumbnails, it's still empty

OBSERVED RESULT
thumbnail cache remains empty

EXPECTED RESULT
thumnails should be saved to the cache

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.1

ADDITIONAL INFORMATION

Comment 1 ipha 2024-07-05 01:07:02 UTC

This issue only seems to appear when ~/.cache is a btrfs subvolume.

Comment 2 Kody 2024-11-29 13:46:27 UTC

This is happening to me, too. I think it's been happening for a long time for me, since I've noticed Dolphin regenerating thumbnails whenever I'd enter directories for a good while, but didn't look into it until now.

Operating System: Arch Linux 
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.12.1-arch1-1 (64-bit)
Graphics Platform: Wayland

Comment 3 aristsakas 2025-12-28 20:34:19 UTC

*** Bug 489762 has been marked as a duplicate of this bug. ***

Comment 4 aristsakas 2025-12-28 20:34:32 UTC

*** Bug 513325 has been marked as a duplicate of this bug. ***

Comment 5 andy 2026-02-01 22:25:31 UTC

This is annoying enough I hacked on a work-around patch, essentially needing to ignore `.isLocalFile()` in KFileItemModelRolesUpdater::startPreviewJob() and possibly KFileItemModelRolesUpdater::loadNextHoverSequencePreview().

I'd appreciate either a setting to always write thumbnails and ignore any "security benefits" (I can manage on my own, especially if using containers, bwrap, bind mounts, etc.) or better detection of acceptable "local" partitions including allowing tmpfs home folder, allowing thumbnailing anything in bind mounts, /mnt, or any mount points derived from permanent drives with luks containers, ZFS, LVM, etc.

```
diff --git a/src/kitemviews/kfileitemmodelrolesupdater.cpp b/src/kitemviews/kfileitemmodelrolesupdater.cpp
index 679370455..ffb9ac1e1 100644
--- a/src/kitemviews/kfileitemmodelrolesupdater.cpp
+++ b/src/kitemviews/kfileitemmodelrolesupdater.cpp
@@ -984,7 +984,7 @@ void KFileItemModelRolesUpdater::startPreviewJob()
 
     KIO::PreviewJob *job = new KIO::PreviewJob(items, cacheSize(), &m_enabledPlugins);
     job->setDevicePixelRatio(m_devicePixelRatio);
-    job->setIgnoreMaximumSize(referenceItem.isLocalFile() && !referenceItem.isSlow() && m_localFileSizePreviewLimit <= 0);
+    job->setIgnoreMaximumSize(!referenceItem.isSlow() && m_localFileSizePreviewLimit <= 0);
     if (job->uiDelegate()) {
         KJobWidgets::setWindow(job, qApp->activeWindow());
     }
@@ -1093,7 +1093,7 @@ void KFileItemModelRolesUpdater::loadNextHoverSequencePreview()
     KIO::PreviewJob *job = new KIO::PreviewJob({m_hoverSequenceItem}, cacheSize(), &m_enabledPlugins);
 
     job->setSequenceIndex(loadSeqIdx);
-    job->setIgnoreMaximumSize(m_hoverSequenceItem.isLocalFile() && !m_hoverSequenceItem.isSlow() && m_localFileSizePreviewLimit <= 0);
+    job->setIgnoreMaximumSize(!m_hoverSequenceItem.isSlow() && m_localFileSizePreviewLimit <= 0);
     if (job->uiDelegate()) {
         KJobWidgets::setWindow(job, qApp->activeWindow());
     }
```