Messages in this thread Patch in this message |  | | Date | Mon, 6 Apr 2026 21:52:16 +0200 | | From | Helge Deller <> | | Subject | [RFC] [PATCH] Fix warning at fs/dcache.c:430 dentry_free |
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The debian buildd servers for the parisc architecture crash reproduceably when building the webkit2gtk debian package, shortly after having shown the warning below.
This patch keeps the lock of the dentry up until when the dentry is given back to the cache and after having freed the "external dentry name".
I'm not sure if this patch is really correct, but it seems to have fixed the problem, although more testing is needed.
kernel: WARNING: CPU: 2 PID: 65 at fs/dcache.c:430 dentry_free+0x15c/0x188 kernel: Modules linked in: binfmt_misc ipmi_si ipmi_devintf ipmi_msghandler sg configfs nfnetlink autofs4 ex> kernel: CPU: 2 UID: 0 PID: 65 Comm: kswapd0 Tainted: G W 6.18.15+deb14-parisc64 #1 NONE De> kernel: Hardware name: 9000/800/rp4440 kernel: kernel: IAOQ[0]: dentry_free+0x15c/0x188 kernel: IAOQ[1]: dentry_free+0x160/0x188 kernel: RP(r2): __dentry_kill+0x2a4/0x338 kernel: Backtrace: kernel: [<00000000408d9eb0>] __dentry_kill+0x2a4/0x338 kernel: [<00000000408dc270>] shrink_dentry_list+0xfc/0x1d0 kernel: [<00000000408dcae4>] prune_dcache_sb+0x88/0xc0 kernel: [<00000000408a6410>] super_cache_scan+0x2bc/0x440 kernel: [<0000000040742f38>] do_shrink_slab+0x254/0x610 kernel: [<00000000407449b4>] shrink_slab+0x4d8/0x860 kernel: [<000000004073948c>] shrink_one+0x108/0x468 kernel: [<000000004073f270>] shrink_node+0xfdc/0x17a0 kernel: [<000000004074016c>] balance_pgdat+0x738/0xfb0 kernel: [<0000000040740da4>] kswapd+0x3c0/0x788 kernel: [<00000000403b35cc>] kthread+0x230/0x430 kernel: [<000000004031d020>] ret_from_kernel_thread+0x20/0x28
Signed-off-by: Helge Deller <deller@gmx.de>
diff --git a/fs/dcache.c b/fs/dcache.c index 7ba1801d8132..c1123787d3bd 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -343,6 +343,7 @@ static void __d_free(struct rcu_head *head) { struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); + spin_unlock(&dentry->d_lock); kmem_cache_free(dentry_cache, dentry); } @@ -350,6 +351,7 @@ static void __d_free_external(struct rcu_head *head) { struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); kfree(external_name(dentry)); + spin_unlock(&dentry->d_lock); kmem_cache_free(dentry_cache, dentry); } @@ -684,9 +686,10 @@ static struct dentry *__dentry_kill(struct dentry *dentry) dentry_unlist(dentry); if (dentry->d_flags & DCACHE_SHRINK_LIST) can_free = false; - spin_unlock(&dentry->d_lock); if (likely(can_free)) dentry_free(dentry); + else + spin_unlock(&dentry->d_lock); if (parent && --parent->d_lockref.count) { spin_unlock(&parent->d_lock); return NULL; @@ -1165,9 +1168,10 @@ void shrink_dentry_list(struct list_head *list) rcu_read_unlock(); d_shrink_del(dentry); can_free = dentry->d_flags & DCACHE_DENTRY_KILLED; - spin_unlock(&dentry->d_lock); if (can_free) dentry_free(dentry); + else + spin_unlock(&dentry->d_lock); continue; } d_shrink_del(dentry);
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