I do more test, it is android esdfs or sdcardfs /storage/emulated/0/Android/data problem, "ext4: Stop providing .writepage hook" cause /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.0 /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.1 /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.idx unable read, on linux 6.4, i use mount bind data/media on storage/emulated, chmod -R 0777 /data/media/0, rm /storage/emulated/0/Android/data/com.android.gallery3d/cache/*, open gallery app can read pictures thumbnail, /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.idx /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.0 /storage/emulated/0/Android/data/com.android.gallery3d/cache/imgcache.1 available read. 2023-05-10 13:17 GMT+08:00, youling 257 <youling257@xxxxxxxxx>: > It isn't android storage emulated esdfs or sdcardfs problem, i test > mount bind /data/media on /storage/emulated, can reproduce my problem. > Let me say clear my problem, "ext4: Stop providing .writepage hook" > cause android gallery app unable read pictures thumbnails. > > I test linux kernel 6.3 Revert "ext4: Stop providing .writepage hook", > android gallery can read pictures thumbnails, > > this is mount bind /data/media on /storage/emulated > /dev/nvme0n1p1 on /storage/emulated type ext4 (rw,seclabel,noatime) > /dev/nvme0n1p1 on /mnt/runtime/default/emulated type ext4 > (rw,seclabel,noatime) > /dev/nvme0n1p1 on /mnt/runtime/read/emulated type ext4 > (rw,seclabel,noatime) > /dev/nvme0n1p1 on /mnt/runtime/write/emulated type ext4 > (rw,seclabel,noatime) > /dev/nvme0n1p1 on /mnt/runtime/full/emulated type ext4 > (rw,seclabel,noatime) > > this is esdfs, > /data/media on /mnt/runtime/default/emulated type esdfs > (rw,nosuid,nodev,noexec,noatime,lower=1023:1023:664:775,upper=0:1015:771:771,derive=multi,noconfine,derive_gid,default_normal,unshared_obb) > /data/media on /storage/emulated type esdfs > (rw,nosuid,nodev,noexec,noatime,lower=1023:1023:664:775,upper=0:1015:771:771,derive=multi,noconfine,derive_gid,default_normal,unshared_obb) > /data/media on /mnt/runtime/read/emulated type esdfs > (rw,nosuid,nodev,noexec,noatime,lower=1023:1023:664:775,upper=0:9997:750:750,derive=multi,noconfine,derive_gid,default_normal,unshared_obb) > /data/media on /mnt/runtime/write/emulated type esdfs > (rw,nosuid,nodev,noexec,noatime,lower=1023:1023:664:775,upper=0:9997:770:770,derive=multi,noconfine,derive_gid,default_normal,unshared_obb) > /data/media on /mnt/runtime/full/emulated type esdfs > (rw,nosuid,nodev,noexec,noatime,lower=1023:1023:664:775,upper=0:9997:770:770,derive=multi,noconfine,derive_gid,default_normal,unshared_obb) > > if i do mount bind data/media on storage/emulated, take a screenshot, > will create > /data/media/0/Pictures/Screenshots/Screenshot_20230510-130020.png > file, > chmod -R 0777 /data/media/0/Pictures/Screenshots, > on linux 6.3 Revert "ext4: Stop providing .writepage hook", android > gallery app can read > /storage/emulated/0/Pictures/Screenshots/Screenshot_20230510-130020.png > thumbnail, > linux 6.4 removed .writepage hook, android gallery unable read thumbnail. > > > 2023-05-10 2:36 GMT+08:00, Theodore Ts'o <tytso@xxxxxxx>: >> On Mon, May 08, 2023 at 10:02:27PM -0700, Eric Biggers wrote: >>> On Tue, May 09, 2023 at 01:51:08AM +0800, youling257 wrote: >>> > I using linux mainline kernel on android. >>> > https://github.com/youling257/android-mainline/commits/6.4 >>> > https://github.com/youling257/android-mainline/commits/6.3 >>> > "ext4: Stop providing .writepage hook" cause some android app unable >>> > to >>> > read storage/emulated/0 files, i need to say android esdfs file system >>> > storage/emulated is ext4 data/media bind mount. >>> > I want to ask, why android storage/emulated need .writepage hook? >>> >>> "esdfs" doesn't exist upstream, so linux-ext4 can't provide support for >>> it. >>> >>> Also, it doesn't exist in the Android Common Kernels either, so the >>> Android team >>> cannot help you either. >> >> The problem with esdfs is that it's based on the old stackable file >> system paradigm which is filled with races and is inherently >> unreliable (just for fun, try running fsstress on the upper and lower >> file systems of a stackable file system simultaneously, and watch the >> kernel crash and burn). For that reason, some number of us have been >> working for a while to eliminate the need for stacking file systems, >> such as sdcardfs. esdfs, etc. from the Android kernel. >> >> The other thing I would add is that upstream has been working[1] on >> getting rid of writepage function. So out-of-tree file systems are >> going to need to adapt --- or die. >> >> [1] https://lore.kernel.org/all/20221202102644.770505-1-hch@xxxxxx/ >> >> It looks like esdfs is coming from the Chromium kernel? The latest >> Chromium kernel I can find is 5.15 based, and it has esdfs in it. I'm >> sad to see that esdfs hasn't been removed from the Chromium kernel >> yet, and replaced with something more stable and reliable, but maybe >> we can find someone who is more familiar with the Chromium kernel to >> comment. >> >> Cheers, >> >> - Ted >> >
