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charset=us-ascii Content-Disposition: inline In-Reply-To: <20240328140330.4747-1-urezki@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 X-Rspamd-Queue-Id: 1E3DD2000C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 7rg4crx1edcggwsej1pzjxshzqtges74 X-HE-Tag: 1711698299-706973 X-HE-Meta: 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 ETdHt//9 Yik52wk947Y5dECnPj5AhsczQTMgpynd85pV1OUQhLNC7qU8x76k8D0zr45BHjvEQZ2egeerTSr/7apZierPfy/nNS2CvDkoPqbGcblWBPNz3qPhvfFIa3nTPh6fwAG5AGA1aPIRgAs+o5daq1EYsKA93i36udpTk9ogGc0u8+xsPd/buc4C95liEB9usmUvj1Gn61sOH4opHRUqPpZpxAap7cGMlZbKh6ePfsaBJWKeOl2pLgjFKoFCZnITYHajjV7KfigpCzimpnVa54PuUmiIbW0CxAASxGOodbQh7vHqLbjEl+Eh55QxMqg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/28/24 at 03:03pm, Uladzislau Rezki (Sony) wrote: > A lockdep reports a possible deadlock in the find_vmap_area_exceed_addr_lock() > function: > > ============================================ > WARNING: possible recursive locking detected > 6.9.0-rc1-00060-ged3ccc57b108-dirty #6140 Not tainted > -------------------------------------------- > drgn/455 is trying to acquire lock: > ffff0000c00131d0 (&vn->busy.lock/1){+.+.}-{2:2}, at: find_vmap_area_exceed_addr_lock+0x64/0x124 > > but task is already holding lock: > ffff0000c0011878 (&vn->busy.lock/1){+.+.}-{2:2}, at: find_vmap_area_exceed_addr_lock+0x64/0x124 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&vn->busy.lock/1); > lock(&vn->busy.lock/1); > > *** DEADLOCK *** > > indeed it can happen if the find_vmap_area_exceed_addr_lock() > gets called concurrently because it tries to acquire two nodes > locks. It was done to prevent removing a lowest VA found on a > previous step. > > To address this a lowest VA is found first without holding a > node lock where it resides. As a last step we check if a VA > still there because it can go away, if removed, proceed with > next lowest. > > Fixes: 53becf32aec1 ("mm: vmalloc: support multiple nodes in vread_iter") > Tested-by: Jens Axboe > Tested-by: Omar Sandoval > Reported-by: Jens Axboe > Signed-off-by: Uladzislau Rezki (Sony) > --- > mm/vmalloc.c | 74 +++++++++++++++++++++++++++++++--------------------- > 1 file changed, 44 insertions(+), 30 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index e94ce4562805..a5a5dfc3843e 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -989,6 +989,27 @@ unsigned long vmalloc_nr_pages(void) > return atomic_long_read(&nr_vmalloc_pages); > } > > +static struct vmap_area *__find_vmap_area(unsigned long addr, struct rb_root *root) > +{ > + struct rb_node *n = root->rb_node; > + > + addr = (unsigned long)kasan_reset_tag((void *)addr); > + > + while (n) { > + struct vmap_area *va; > + > + va = rb_entry(n, struct vmap_area, rb_node); > + if (addr < va->va_start) > + n = n->rb_left; > + else if (addr >= va->va_end) > + n = n->rb_right; > + else > + return va; > + } > + > + return NULL; > +} > + > /* Look up the first VA which satisfies addr < va_end, NULL if none. */ > static struct vmap_area * > __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) > @@ -1025,47 +1046,40 @@ __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) > static struct vmap_node * > find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) > { > - struct vmap_node *vn, *va_node = NULL; > - struct vmap_area *va_lowest; > + unsigned long va_start_lowest; > + struct vmap_node *vn; > int i; > > - for (i = 0; i < nr_vmap_nodes; i++) { > +repeat: > + for (i = 0, va_start_lowest = 0; i < nr_vmap_nodes; i++) { > vn = &vmap_nodes[i]; > > spin_lock(&vn->busy.lock); > - va_lowest = __find_vmap_area_exceed_addr(addr, &vn->busy.root); > - if (va_lowest) { > - if (!va_node || va_lowest->va_start < (*va)->va_start) { > - if (va_node) > - spin_unlock(&va_node->busy.lock); > - > - *va = va_lowest; > - va_node = vn; > - continue; > - } > - } > + *va = __find_vmap_area_exceed_addr(addr, &vn->busy.root); > + > + if (*va) > + if (!va_start_lowest || (*va)->va_start < va_start_lowest) > + va_start_lowest = (*va)->va_start; How about below change about va_start_lowest? Personal preference, not strong opinion. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 9b1a41e12d70..bd6a66c54ad2 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1046,19 +1046,19 @@ __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) static struct vmap_node * find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) { - unsigned long va_start_lowest; + unsigned long va_start_lowest = ULONG_MAX; struct vmap_node *vn; int i; repeat: - for (i = 0, va_start_lowest = 0; i < nr_vmap_nodes; i++) { + for (i = 0; i < nr_vmap_nodes; i++) { vn = &vmap_nodes[i]; spin_lock(&vn->busy.lock); *va = __find_vmap_area_exceed_addr(addr, &vn->busy.root); if (*va) - if (!va_start_lowest || (*va)->va_start < va_start_lowest) + if ((*va)->va_start < va_start_lowest) va_start_lowest = (*va)->va_start; spin_unlock(&vn->busy.lock); } @@ -1069,7 +1069,7 @@ find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) * been removed concurrently thus we need to proceed * with next one what is a rare case. */ - if (va_start_lowest) { + if (va_start_lowest != ULONG_MAX) { vn = addr_to_node(va_start_lowest); spin_lock(&vn->busy.lock); > spin_unlock(&vn->busy.lock); > } > > - return va_node; > -} > - > -static struct vmap_area *__find_vmap_area(unsigned long addr, struct rb_root *root) > -{ > - struct rb_node *n = root->rb_node; > + /* > + * Check if found VA exists, it might it is gone away. ~~~~ grammer mistake? > + * In this case we repeat the search because a VA has > + * been removed concurrently thus we need to proceed > + * with next one what is a rare case. ~~~~ typo, which? > + */ > + if (va_start_lowest) { > + vn = addr_to_node(va_start_lowest); > > - addr = (unsigned long)kasan_reset_tag((void *)addr); > + spin_lock(&vn->busy.lock); > + *va = __find_vmap_area(va_start_lowest, &vn->busy.root); > > - while (n) { > - struct vmap_area *va; > + if (*va) > + return vn; > > - va = rb_entry(n, struct vmap_area, rb_node); > - if (addr < va->va_start) > - n = n->rb_left; > - else if (addr >= va->va_end) > - n = n->rb_right; > - else > - return va; > + spin_unlock(&vn->busy.lock); > + goto repeat; > } Other than above nickpick concerns, this looks good to me. Reviewed-by: Baoquan He