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([2600:1700:6476:1430:2f9f:a96f:bcb:6021]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b2b714bd40sm60952257b3.16.2026.11.02.14.17.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 14:17:09 -0800 (PST) Message-ID: <92845c60aca5dc2209a43d309b7bb9fa66aa044e.camel@dubeyko.com> Subject: Re: [PATCH] hfsplus: free failed b-tree nodes in hfs_bnode_put() From: Viacheslav Dubeyko To: Song jeonghak , Markus Elfring , John Paul Adrian Glaubitz , Yangtao Li , linux-fsdevel@vger.kernel.org Cc: LKML , Edward Adam Davis , Shardul Bankar , syzbot+98547b0428b6a6a3467c@syzkaller.appspotmail.com Date: Mon, 02 Nov 2026 14:17:07 -0800 In-Reply-To: <20261101162949.147400-1-thdwjdgkr123@gmail.com> References: <773c7445-8d4b-4d94-a995-297ecee9c879@web.de> <20261101162949.147400-1-thdwjdgkr123@gmail.com> Autocrypt: addr=slava@dubeyko.com; prefer-encrypt=mutual; keydata=mQINBGgaTLYBEADaJc/WqWTeunGetXyyGJ5Za7b23M/ozuDCWCp+yWUa2GqQKH40dxRIR zshgOmAue7t9RQJU9lxZ4ZHWbi1Hzz85+0omefEdAKFmxTO6+CYV0g/sapU0wPJws3sC2Pbda9/eJ ZcvScAX2n/PlhpTnzJKf3JkHh3nM1ACO3jzSe2/muSQJvqMLG2D71ccekr1RyUh8V+OZdrPtfkDam V6GOT6IvyE+d+55fzmo20nJKecvbyvdikWwZvjjCENsG9qOf3TcCJ9DDYwjyYe1To8b+mQM9nHcxp jUsUuH074BhISFwt99/htZdSgp4csiGeXr8f9BEotRB6+kjMBHaiJ6B7BIlDmlffyR4f3oR/5hxgy dvIxMocqyc03xVyM6tA4ZrshKkwDgZIFEKkx37ec22ZJczNwGywKQW2TGXUTZVbdooiG4tXbRBLxe ga/NTZ52ZdEkSxAUGw/l0y0InTtdDIWvfUT+WXtQcEPRBE6HHhoeFehLzWL/o7w5Hog+0hXhNjqte fzKpI2fWmYzoIb6ueNmE/8sP9fWXo6Av9m8B5hRvF/hVWfEysr/2LSqN+xjt9NEbg8WNRMLy/Y0MS p5fgf9pmGF78waFiBvgZIQNuQnHrM+0BmYOhR0JKoHjt7r5wLyNiKFc8b7xXndyCDYfniO3ljbr0j tXWRGxx4to6FwARAQABtCZWaWFjaGVzbGF2IER1YmV5a28gPHNsYXZhQGR1YmV5a28uY29tPokCVw QTAQoAQQIbAQUJA8JnAAULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBFXDC2tnzsoLQtrbBDlc2cL fhEB1BQJoGl5PAhkBAAoJEDlc2cLfhEB17DsP/jy/Dx19MtxWOniPqpQf2s65enkDZuMIQ94jSg7B F2qTKIbNR9SmsczjyjC+/J7m7WZRmcqnwFYMOyNfh12aF2WhjT7p5xEAbvfGVYwUpUrg/lcacdT0D Yk61GGc5ZB89OAWHLr0FJjI54bd7kn7E/JRQF4dqNsxU8qcPXQ0wLHxTHUPZu/w5Zu/cO+lQ3H0Pj pSEGaTAh+tBYGSvQ4YPYBcV8+qjTxzeNwkw4ARza8EjTwWKP2jWAfA/ay4VobRfqNQ2zLoo84qDtN Uxe0zPE2wobIXELWkbuW/6hoQFPpMlJWz+mbvVms57NAA1HO8F5c1SLFaJ6dN0AQbxrHi45/cQXla 9hSEOJjxcEnJG/ZmcomYHFneM9K1p1K6HcGajiY2BFWkVet9vuHygkLWXVYZ0lr1paLFR52S7T+cf 6dkxOqu1ZiRegvFoyzBUzlLh/elgp3tWUfG2VmJD3lGpB3m5ZhwQ3rFpK8A7cKzgKjwPp61Me0o9z HX53THoG+QG+o0nnIKK7M8+coToTSyznYoq9C3eKeM/J97x9+h9tbizaeUQvWzQOgG8myUJ5u5Dr4 6tv9KXrOJy0iy/dcyreMYV5lwODaFfOeA4Lbnn5vRn9OjuMg1PFhCi3yMI4lA4umXFw0V2/OI5rgW BQELhfvW6mxkihkl6KLZX8m1zcHitCpWaWFjaGVzbGF2IER1YmV5a28gPFNsYXZhLkR1YmV5a29Aa WJtLmNvbT6JAlQEEwEKAD4WIQRVwwtrZ87KC0La2wQ5XNnC34RAdQUCaBpd7AIbAQUJA8JnAAULCQ gHAgYVCgkICwIEFgIDAQIeAQIXgAAKCRA5XNnC34RAdYjFEACiWBEybMt1xjRbEgaZ3UP5i2bSway DwYDvgWW5EbRP7JcqOcZ2vkJwrK3gsqC3FKpjOPh7ecE0I4vrabH1Qobe2N8B2Y396z24mGnkTBbb 16Uz3PC93nFN1BA0wuOjlr1/oOTy5gBY563vybhnXPfSEUcXRd28jI7z8tRyzXh2tL8ZLdv1u4vQ8 E0O7lVJ55p9yGxbwgb5vXU4T2irqRKLxRvU80rZIXoEM7zLf5r7RaRxgwjTKdu6rYMUOfoyEQQZTD 4Xg9YE/X8pZzcbYFs4IlscyK6cXU0pjwr2ssjearOLLDJ7ygvfOiOuCZL+6zHRunLwq2JH/RmwuLV mWWSbgosZD6c5+wu6DxV15y7zZaR3NFPOR5ErpCFUorKzBO1nA4dwOAbNym9OGkhRgLAyxwpea0V0 ZlStfp0kfVaSZYo7PXd8Bbtyjali0niBjPpEVZdgtVUpBlPr97jBYZ+L5GF3hd6WJFbEYgj+5Af7C UjbX9DHweGQ/tdXWRnJHRzorxzjOS3003ddRnPtQDDN3Z/XzdAZwQAs0RqqXrTeeJrLppFUbAP+HZ TyOLVJcAAlVQROoq8PbM3ZKIaOygjj6Yw0emJi1D9OsN2UKjoe4W185vamFWX4Ba41jmCPrYJWAWH fAMjjkInIPg7RLGs8FiwxfcpkILP0YbVWHiNAabQoVmlhY2hlc2xhdiBEdWJleWtvIDx2ZHViZXlr b0BrZXJuZWwub3JnPokCVAQTAQoAPhYhBFXDC2tnzsoLQtrbBDlc2cLfhEB1BQJoVemuAhsBBQkDw mcABQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEDlc2cLfhEB1GRwP/1scX5HO9Sk7dRicLD/fxo ipwEs+UbeA0/TM8OQfdRI4C/tFBYbQCR7lD05dfq8VsYLEyrgeLqP/iRhabLky8LTaEdwoAqPDc/O 9HRffx/faJZqkKc1dZryjqS6b8NExhKOVWmDqN357+Cl/H4hT9wnvjCj1YEqXIxSd/2Pc8+yw/KRC AP7jtRzXHcc/49Lpz/NU5irScusxy2GLKa5o/13jFK3F1fWX1wsOJF8NlTx3rLtBy4GWHITwkBmu8 zI4qcJGp7eudI0l4xmIKKQWanEhVdzBm5UnfyLIa7gQ2T48UbxJlWnMhLxMPrxgtC4Kos1G3zovEy Ep+fJN7D1pwN9aR36jVKvRsX7V4leIDWGzCdfw1FGWkMUfrRwgIl6i3wgqcCP6r9YSWVQYXdmwdMu 1RFLC44iF9340S0hw9+30yGP8TWwd1mm8V/+zsdDAFAoAwisi5QLLkQnEsJSgLzJ9daAsE8KjMthv hUWHdpiUSjyCpigT+KPl9YunZhyrC1jZXERCDPCQVYgaPt+Xbhdjcem/ykv8UVIDAGVXjuk4OW8la nf8SP+uxkTTDKcPHOa5rYRaeNj7T/NClRSd4z6aV3F6pKEJnEGvv/DFMXtSHlbylhyiGKN2Amd0b4 9jg+DW85oNN7q2UYzYuPwkHsFFq5iyF1QggiwYYTpoVXsw Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (by Flathub.org) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Mon, 2026-11-02 at 01:29 +0900, Song jeonghak wrote: > Hi Markus, >=20 > (Resending as plain text; my previous reply was rejected by the lists > because it contained an HTML part. Sorry for the duplicate.) >=20 > > How do you think about to avoid a bit of duplicate source code? >=20 > Thanks for looking at the patch. The two branches share the > unhash/unlock/free steps, but they handle different situations: >=20 > =C2=A0- HFS_BNODE_DELETED is only set by hfs_bnode_unlink(), when the nod= e > =C2=A0=C2=A0 is removed from the tree. Its slot becomes unused, so > =C2=A0=C2=A0 hfs_bnode_put() also clears its bit in the allocation map > =C2=A0=C2=A0 (hfs_bmap_free()) and, if HFSPLUS_VOL_UNUSED_NODE_FIX is set= , > =C2=A0=C2=A0 zeroes it (hfs_bnode_clear()). >=20 > =C2=A0- HFS_BNODE_ERROR means the node failed to load. It is still part o= f > =C2=A0=C2=A0 the on-disk tree; only the in-memory copy is dropped. Its ma= p bit > =C2=A0=C2=A0 must stay set, otherwise the allocator could hand out a node= that > =C2=A0=C2=A0 is still linked, and its on-disk contents should not be > =C2=A0=C2=A0 overwritten. In my reproduction the failing node is the head= er > =C2=A0=C2=A0 node (node 0), which must always stay allocated. From readin= g the > =C2=A0=C2=A0 code, hfs_bmap_free() would hit its BUG_ON(!node->this) for = it; > =C2=A0=C2=A0 I have not run that. >=20 > I looked at how other put functions that take the lock with > atomic_dec_and_lock()/refcount_dec_and_lock() deal with this, and > both forms are used. ceph_put_snap_realm() in fs/ceph/snap.c repeats > the unlock in each branch, while fsnotify_put_mark() in > fs/notify/mark.c records the difference in a flag and does the common > part once. Following the second style, the two branches could become: >=20 > bool deleted =3D test_bit(HFS_BNODE_DELETED, &node- > >flags); >=20 > if (deleted || test_bit(HFS_BNODE_ERROR, &node- > >flags)) { > hfs_bnode_unhash(node); > spin_unlock(&tree->hash_lock); > if (deleted) { > if (hfs_bnode_need_zeroout(tree)) > hfs_bnode_clear(node, 0, > tree->node_size); > hfs_bmap_free(node); > } > hfs_bnode_free(node); > return; > } > spin_unlock(&tree->hash_lock); >=20 > I am fine with either form and will use whichever the maintainers > prefer in v2. >=20 > While looking into this I found a mistake in my changelog. It says a > failed node "has no b-tree map bit to release and no contents to zero > out". That is wrong: the bit is set and the contents are on disk. > They > are left alone on purpose, as described above. I will correct this in > v2. >=20 >=20 Somehow I cannot find the patch in my email client. Please, double check that you send the patch in plain text and, please, ping me if I don't answer on v2 of the patch. Thanks, Slava.