Created attachment 183513 [details] Folder with and without a thumbnail SUMMARY If a folder is situated on a bcachefs partition its icon in Dolphin will not display thumbnails of its contents regardless of the preview options. STEPS TO REPRODUCE 1. Setup the environment. > $ touch fs && truncate fs --size 128M && mkfs.bcachefs fs && sudo mount fs /mnt && sudo chown $USER:$USER /mnt && mkdir /mnt/folder && cp /usr/share/plasma/avatars/photos/Dog.png /mnt/folder/picture.png 2. Open the Dolphin file manager. 3. Enable previews for folders and pictures. 4. Open the `/mnt` directory. Alternatively 2. Compile KIO with `cmake -DBUILD_TESTING=ON ...` 3. Run `build/bin/previewtest` 4. Select `/mnt/folder` and press `Generate` OBSERVED RESULT Icon of `/mnt/folder` keeps its stock appearance. `build/bin/previewtest` displays `failed`. EXPECTED RESULT Folder `/mnt/folder` has on overlaid thumbnail of `/mnt/folder/picture.png` on its icon. `build/bin/previewtest` displays an icon. SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 6.4.3 KDE Frameworks Version: 6.16.0 Qt Version: 6.9.1 Kernel Version: 6.15.7-zen1-1-zen (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 5600G with Radeon Graphics Memory: 32 GiB of RAM (27.3 GiB usable) Graphics Processor: AMD Radeon Graphics ADDITIONAL INFORMATION The cause of this bug is a file size check at https://invent.kde.org/frameworks/kio/-/blob/v6.16.0/src/gui/previewjob.cpp?ref_type=tags#L580 > const KIO::filesize_t size = static_cast<KIO::filesize_t>(statResult.numberValue(KIO::UDSEntry::UDS_SIZE, 0)); > if (size == 0) { > qCDebug(KIO_GUI) << "PreviewJob: skipping an empty file, migth be a broken symlink" << d->currentItem.item.url(); > d->determineNextFile(); > return; > } It seems on bcachefs stat'ing any folder results in the reported size always being 0. > $ stat /mnt/folder > File: /mnt/folder > Size: 0 Blocks: 0 IO Block: 4096 directory > Device: 253,0 Inode: 74608 Links: 2 > Access: (0755/drwxr-xr-x) Uid: ( 1000/ user) Gid: ( 1000/ group) > Access: 2025-07-25 XX:XX:XX.XXXXXXXXX -XXXX > Modify: 2025-07-25 XX:XX:XX.XXXXXXXXX +XXXX > Change: 2025-07-25 XX:XX:XX.XXXXXXXXX -XXXX > Birth: 2025-07-25 XX:XX:XX.XXXXXXXXX +XXXX Commenting out the above size check restores the folder thumbnails. I have also checked and the bug is still present on the master branch (f60be14b9ed1b90273d1ef9e2ed145afdd3db6e9) in file https://invent.kde.org/frameworks/kio/-/blob/master/src/gui/filepreviewjob.cpp#L160
Maybe it's related to this bug? https://bugs.kde.org/show_bug.cgi?id=501882
> It seems on bcachefs stat'ing any folder results in the reported size always being 0. This seems to be true with folders on an SMB share (mounted with cifs). I think you found the culprit why this affects SMB also. :)
I believe since the bug is the same and the factors that determine it are the same (which affects SMB and bcachefs, and anywhere else that a folder's size is "0"), this can be marked as a duplicate of the bug from 5 months ago: https://bugs.kde.org/show_bug.cgi?id=501882
*** This bug has been marked as a duplicate of bug 501882 ***
Created a merge request at https://invent.kde.org/frameworks/kio/-/merge_requests/2004
Git commit 8a713b01dd94027a8869b8dc417af162f61abac2 by Méven Car, on behalf of Mikhail Morozov. Committed on 24/09/2025 at 08:39. Pushed by meven into branch 'master'. filepreviewjob: Don't apply size check to directories If a folder is situated on a bcachefs partition (or any other directory with 0 sized directory entry) its icon in Dolphin will not display thumbnails of its contents regardless of the preview options. Judging by the log line `"PreviewJob: skipping an empty file, migth be a broken symlink"`, the size check should only apply to files not folders. Related: bug 501882 M +2 -2 src/gui/filepreviewjob.cpp https://invent.kde.org/frameworks/kio/-/commit/8a713b01dd94027a8869b8dc417af162f61abac2