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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?U50Rc8KRYaYfRwOWtQ0giI4EPfp1L3Yj1bwxH2b+6uvghJe1p26HVA5USN5L?= =?us-ascii?Q?d9dAH6L7Qr/R9oBTtU9vcTQPgx2BtmInbA+RamjoweTo/SE0ot+QnJmHz/+U?= =?us-ascii?Q?GVP8KTC9ANYoN5DKCg2ttrG4kgT8tZqf+Nw/q+ORTPWfZRqK/jFR6cuiXFE1?= =?us-ascii?Q?Ep0jyAmrD8x8i8l78SwdZo6N9MsHZ4S3pO1yGUX67tYLz2YnakZpWsvaBPpT?= =?us-ascii?Q?NEdEbPjHpf0XeLXR3Cmev7eRKoiIGup+VxJKYodv3u6oeeJSjNHUhQD6Ld+1?= =?us-ascii?Q?b3S2XRc35KfEr79igmAcePQQHlNXa+2ONw1IHQyQTrvOPC8Oa2Q4F5hk4J0T?= =?us-ascii?Q?t8rblVNltkScSnzHa8cUO292zbyS1ZviCKYagW9RMYNR3S597CyGqFm86Mq2?= =?us-ascii?Q?5sh6W407zxuRY3nU2sGKY02S539GuybSWxQQea7e6m+5SBrdY/F1AZnKL4U0?= =?us-ascii?Q?7FLN/gWYXgnsFS7W4ReWpjN/iJTSFFc6EQWeHrG//hmVMqtrQQFHRQsjmZSz?= =?us-ascii?Q?jZ73irstC98B/pBT6EYYZW9vsAutRXNCAotJTiyY3sD8X48A7qjFa2h9WCjq?= =?us-ascii?Q?1J7Zk9jb02fdqDCOhyvVlKPaG1rP8+jmXpYNWCA4Zo0KXt81jnDL5mk2ESGs?= =?us-ascii?Q?u6jMIYgBOnAFYnXsQzFz8sREon99JyHBJFdJ4yaGFaG2sPJBR2gI+RjLmg6f?= =?us-ascii?Q?7Mzuex9J+MAzG+PCuqYrTv0ym/ojb1dZ533RffoclK2HDhWu2JZU3SvFc/jt?= =?us-ascii?Q?e+6Z9TD+hUWJ3LRFyc5dbCuMy0JwinMVBiSGK7vbvyRThmTxlPPO0mKE5IVa?= =?us-ascii?Q?slE2+zhqH9s0yb/TsQjzjyXLntpRqr+25pTNlbcc0dtfWlMjbYaU86dPzlvO?= =?us-ascii?Q?w7CAdGvOT2cB70wuFA/5G9aXlNmH8USXtxm4Ub1ikfkrkl0D+XW6ZQTQ2A2p?= =?us-ascii?Q?sD7xMfWVHyFhLbStBtYYUY8VLDiiRbVL7fkozDVdk8JxLTrvokxE4HTwComY?= =?us-ascii?Q?8b4D?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-AuthSource: PA4PR04MB7533.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2021 08:43:33.8544 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-Network-Message-Id: 2b68d7b2-5cfa-4fc6-a3e8-08d8b21f26ee X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: GrUNFVBk/pqqqk//nJH4iVqOiasEcckis6cKZlGshNTbluDDasa4z5o2wubYV/zH X-MS-Exchange-Transport-CrossTenantHeadersStamped: PA4PR04MB7855 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2021/1/6 =E4=B8=8B=E5=8D=884:24, Qu Wenruo wrote: >=20 >=20 > On 2021/1/6 =E4=B8=8A=E5=8D=889:01, Qu Wenruo wrote: >> Unlike the original try_release_extent_buffer, >> try_release_subpage_extent_buffer() will iterate through >> btrfs_subpage::tree_block_bitmap, and try to release each extent buffer. >> >> Signed-off-by: Qu Wenruo >> --- >> =C2=A0 fs/btrfs/extent_io.c | 76 +++++++++++++++++++++++++++++++++++++++= +++++ >> =C2=A0 1 file changed, 76 insertions(+) >> >> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c >> index 194cb8b63216..792264f5c3c2 100644 >> --- a/fs/btrfs/extent_io.c >> +++ b/fs/btrfs/extent_io.c >> @@ -6258,10 +6258,86 @@ void memmove_extent_buffer(const struct=20 >> extent_buffer *dst, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> =C2=A0 } >> +static int try_release_subpage_extent_buffer(struct page *page) >> +{ >> +=C2=A0=C2=A0=C2=A0 struct btrfs_fs_info *fs_info =3D btrfs_sb(page->map= ping->host->i_sb); >> +=C2=A0=C2=A0=C2=A0 u64 page_start =3D page_offset(page); >> +=C2=A0=C2=A0=C2=A0 int bitmap_size =3D BTRFS_SUBPAGE_BITMAP_SIZE; >> +=C2=A0=C2=A0=C2=A0 int bit_start =3D 0; >> +=C2=A0=C2=A0=C2=A0 int ret; >> + >> +=C2=A0=C2=A0=C2=A0 while (bit_start < bitmap_size) { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct btrfs_subpage *subpag= e; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct extent_buffer *eb; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long flags; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 u16 tmp =3D 1 << bit_start; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 u64 start; >> + >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Make sure the page s= till has private, as previous iteration >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * can detach page priv= ate. >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin_lock(&page->mapping->pr= ivate_lock); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!PagePrivate(page)) { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin= _unlock(&page->mapping->private_lock); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 brea= k; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> + >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 subpage =3D (struct btrfs_su= bpage *)page->private; >> + >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin_lock_irqsave(&subpage->= lock, flags); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin_unlock(&page->mapping->= private_lock); >> + >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!(tmp & subpage->tree_bl= ock_bitmap))=C2=A0 { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin= _unlock_irqrestore(&subpage->lock, flags); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bit_= start++; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 cont= inue; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> + >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 start =3D bit_start * fs_inf= o->sectorsize + page_start; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bit_start +=3D fs_info->node= size >> fs_info->sectorsize_bits; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Here we can't call f= ind_extent_buffer() which will increase >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * eb->refs. >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 rcu_read_lock(); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 eb =3D radix_tree_lookup(&fs= _info->buffer_radix, >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 start >> fs_info->sectorsize_bits); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ASSERT(eb); >=20 > Another ASSERT() hit here. Surprised that I have never hit such case=20 > before. >=20 > Since in releasse_extent_buffer(), radix tree is removed first, then=20 > subpage tree_block_bitmap update, we could have cases where subpage=20 > tree_block_bitmap is set but no eb in radix tree. >=20 > In that case, we can safely go next bit and re-check. >=20 > The function return value is only bounded to if the page has private bit= =20 > or not, so here we can safely continue. >=20 > Nik is right on this, we need better eb refs handling refactor, I'll=20 > investigate more time to make the eb refs handling better. The root problem here is, we have too many things to be synchronized for=20 extent buffer. We have eb::refs, eb::bflags (IN_TREE), buffer_radix, and the new=20 subpage::tree_block_bitmap, they all need to be in sync with each other. I'm wondering if we could find a good and clear enough way to handle=20 extent buffers. IMHO, we need to sacrifice some metadata performance (which is already=20 poor enough), or there is really no better way to solve the mess... Thanks, Qu >=20 > Thanks, > Qu >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin_lock(&eb->refs_lock); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (atomic_read(&eb->refs) != =3D 1 || extent_buffer_under_io(eb) || >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 !tes= t_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin= _unlock(&eb->refs_lock); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 rcu_= read_unlock(); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 cont= inue; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 rcu_read_unlock(); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 spin_unlock_irqrestore(&subp= age->lock, flags); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Here we don't care t= he return value, we will always check >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * the page private at = the end. >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * And release_extent_b= uffer() will release the refs_lock. >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 release_extent_buffer(eb); >> +=C2=A0=C2=A0=C2=A0 } >> +=C2=A0=C2=A0=C2=A0 /* Finally to check if we have cleared page private = */ >> +=C2=A0=C2=A0=C2=A0 spin_lock(&page->mapping->private_lock); >> +=C2=A0=C2=A0=C2=A0 if (!PagePrivate(page)) >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D 1; >> +=C2=A0=C2=A0=C2=A0 else >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D 0; >> +=C2=A0=C2=A0=C2=A0 spin_unlock(&page->mapping->private_lock); >> +=C2=A0=C2=A0=C2=A0 return ret; >> + >> +} >> + >> =C2=A0 int try_release_extent_buffer(struct page *page) >> =C2=A0 { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct extent_buffer *eb; >> +=C2=A0=C2=A0=C2=A0 if (btrfs_sb(page->mapping->host->i_sb)->sectorsize = < PAGE_SIZE) >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return try_release_subpage_e= xtent_buffer(page); >> + >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * We need to make sure nobody is at= taching this page to an eb=20 >> right >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * now. >> >=20