On Tue, Jun 23, 2026 at 12:21 PM Yoann Congal <[email protected]> wrote:

> On Wed Jun 10, 2026 at 6:49 PM CEST, Bruce Ashfield via
> lists.openembedded.org wrote:
> > From: Bruce Ashfield <[email protected]>
> >
> > Updating linux-yocto/6.6 to the latest korg -stable release that
> comprises
> > the following commits:
> >
> >     c09fbcd31ae6 Linux 6.6.130
> > [...]
> >     dc7c9b9d03a5 ext4: drop extent cache when splitting extent fails
> >     f0931a5c1700 ext4: drop extent cache after doing PARTIAL_VALID1
> zeroout
> >     67cdb7bd7442 ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting
> before submitting I/O
> >     11406eb96a19 ext4: correct the comments place for
> EXT4_EXT_MAY_ZEROOUT
>
> Hello Bruce,
>
> >     ed0096fc86b2 ext4: get rid of ppath in
> ext4_ext_handle_unwritten_extents()
> >     d7b04ea31c6e ext4: get rid of ppath in
> ext4_ext_convert_to_initialized()
> >     c24ce099bea9 ext4: get rid of ppath in
> ext4_convert_unwritten_extents_endio()
> >     147a6a2725b1 ext4: get rid of ppath in ext4_split_convert_extents()
> >     cda8a34348d7 ext4: get rid of ppath in ext4_split_extent()
> >     58ddae5d77b1 ext4: don't zero the entire extent if
> EXT4_EXT_DATA_PARTIAL_VALID1
> >     e766534911b3 ext4: subdivide EXT4_EXT_DATA_VALID1
> >     ffb68fc57207 ext4: get rid of ppath in ext4_split_extent_at()
> >     fb138df7d886 ext4: get rid of ppath in ext4_ext_insert_extent()
> >     8f6e910852d8 ext4: get rid of ppath in ext4_ext_create_new_leaf()
> >     cafb151eb180 ext4: get rid of ppath in ext4_find_extent()
>
> (The following was found by Gemini, but I've checked it)
>
> Looks like these commits introduced a bug causing an intermittent LTP
> regression:
> https://autobuilder.yoctoproject.org/valkyrie/#/builders/98/builds/3837
> ->
> https://valkyrie.yocto.io/pub/non-release/20260622-121/testresults/qemuarm64-ltp/core-image-sato/qemu_boot_log.20260623002740
>
> [ 6952.500858] Unable to handle kernel paging request at virtual address
> ffffffffffffffec
> [ 6952.503768] Mem abort info:
> [ 6952.504431]   ESR = 0x0000000096000005
> [ 6952.505333]   EC = 0x25: DABT (current EL), IL = 32 bits
> [ 6952.506541]   SET = 0, FnV = 0
> [ 6952.507354]   EA = 0, S1PTW = 0
> [ 6952.508154]   FSC = 0x05: level 1 translation fault
> [ 6952.509208] Data abort info:
> [ 6952.509849]   ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
> [ 6952.511175]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> [ 6952.512372]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> [ 6952.513667] swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000041250000
> [ 6952.514909] [ffffffffffffffec] pgd=0000000000000000,
> p4d=0000000000000000, pud=0000000000000000
> [ 6952.516423] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
> [ 6952.517503] Modules linked in: x_tables tun loop [last unloaded:
> ip6_tables]
> [ 6952.518691] CPU: 1 PID: 1078 Comm: kworker/u12:1 Tainted: G        W
>       6.6.142-yocto-standard #1
> [ 6952.520269] Hardware name: linux,dummy-virt (DT)
> [ 6952.521094] Workqueue: writeback wb_workfn (flush-7:0)
> [ 6952.521985] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS
> BTYPE=--)
> [ 6952.523184] pc : ext4_ext_map_blocks+0x260/0x1860
> [ 6952.524011] lr : ext4_ext_map_blocks+0xdb8/0x1860
> [ 6952.524851] sp : ffffffc086a3b620
> [ 6952.525421] x29: ffffffc086a3b740 x28: ffffffffffffffe4 x27:
> 000000000000808c
> [ 6952.526624] x26: ffffff8017dd9000 x25: 000000000000808c x24:
> 0000000000000002
> [ 6952.527849] x23: ffffff8035e766c8 x22: ffffff802e589690 x21:
> 000000000000042f
> [ 6952.529087] x20: ffffffc086a3b948 x19: ffffff8035e767f0 x18:
> 0000000000000000
> [ 6952.530310] x17: ffffffc081691310 x16: fffffffe001ab548 x15:
> 0000005564d4cb48
> [ 6952.531519] x14: 00000000ffffffff x13: 0000000000000000 x12:
> ffffffffffffffc0
> [ 6952.532683] x11: 0000000000000040 x10: ffffff8005d81d80 x9 :
> ffffffc0803cce14
> [ 6952.533886] x8 : 00000000bab647bc x7 : 0000000000000000 x6 :
> 000000000000d847
> [ 6952.535065] x5 : 0000000000000000 x4 : 0000000000316019 x3 :
> 0000000000000000
> [ 6952.536264] x2 : 0000000000000000 x1 : 0000000000000000 x0 :
> ffffff803deec880
> [ 6952.537425] Call trace:
> [ 6952.537860]  ext4_ext_map_blocks+0x260/0x1860
> [ 6952.538589]  ext4_map_blocks+0x19c/0x598
> [ 6952.539258]  ext4_do_writepages+0x5a4/0xbe0
> [ 6952.539977]  ext4_writepages+0x84/0x110
> [ 6952.540624]  do_writepages+0x94/0x1e0
> [ 6952.541240]  __writeback_single_inode+0x60/0x4d8
> [ 6952.542086]  writeback_sb_inodes+0x208/0x4b0
> [ 6952.542812]  __writeback_inodes_wb+0x58/0x118
> [ 6952.543578]  wb_writeback+0x274/0x440
> [ 6952.544198]  wb_workfn+0x3b0/0x5c8
> [ 6952.544788]  process_one_work+0x16c/0x3e0
> [ 6952.545434]  worker_thread+0x1b4/0x378
> [ 6952.546059]  kthread+0x118/0x128
> [ 6952.546599]  ret_from_fork+0x10/0x20
> [ 6952.547197] Code: 2a0103f9 b9009fe1 b9000e99 b40055fc (79401398)
> [ 6952.548170] ---[ end trace 0000000000000000 ]---
> [ 6952.551090] ------------[ cut here ]------------
>
> Reading the resulting code in 6.6.142:
> fs/ext4/extents.c:
> int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>                         struct ext4_map_blocks *map, int flags)
> {
>         struct ext4_ext_path *path = NULL;
>         // ...
>
> got_allocated_blocks:
>         path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
>         if (IS_ERR(path)) {
>                 err = PTR_ERR(path);
>                 /*
>                  * Gracefully handle out of space conditions. If the
> filesystem
>                  * is inconsistent, we'll just leak allocated blocks to
> avoid
>                  * causing even more damage.
>                  */
>                 // ...
>                 goto out;
>         }
>
>         // ...
> out:
>         ext4_free_ext_path(path);
>
>         trace_ext4_ext_map_blocks_exit(inode, flags, map,
>                                        err ? err : allocated);
>         return err ? err : allocated;
> }
>
> => Under out of space condition (what LTP does a *LOT*): path is given
> unmodified to
> ext4_free_ext_path() that only does a NULL check (no IS_ERR) before
> dereferencing it. And that produces the oops and then, the LTP failure.
>
> Notably, master commit 6b854d552711 ("ext4: get rid of ppath in
> get_ext_path()")
> never got backported to 6.6.y. But does add the IS_ERR_OR_NULL() check
> to ext4_free_ext_path:
>  void ext4_free_ext_path(struct ext4_ext_path *path)
>  {
> +       if (IS_ERR_OR_NULL(path))
> +               return;
>
> Bruce, what do you think? Should we backport
> 6b854d552711·("ext4:·get·rid·of·ppath·in·get_ext_path()")? Ask for it to
> be backported?
>

It's possible. But without being able to reproduce the issues locally, I'm
just
guessing.

I wouldn't just backport it, I'd suggest that -stable pick it up as well,
but then
I'm back to not being able to see any issues locally.  I wouldn't ask for a
backport without knowing it does fix the issues.

I'm happy to cherry-pick it as a shot in the dark, but that's all it would
be :)

Bruce



>
> Thanks for your help!
> --
> Yoann Congal
> Smile ECS
>
>

-- 
- Thou shalt not follow the NULL pointer, for chaos and madness await thee
at its end
- "Use the force Harry" - Gandalf, Star Trek II
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