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Sun, 12 Jan 2025 21:49:42 -0800 (PST) MIME-Version: 1.0 References: <20241230174621.61185-1-ryncsn@gmail.com> <20241230174621.61185-9-ryncsn@gmail.com> In-Reply-To: From: Kairui Song Date: Mon, 13 Jan 2025 13:49:26 +0800 X-Gm-Features: AbW1kvbQYwauWQTMGvKA-4D_LBHmUYOnnnU9XduLNPSVTA6-WGIk8gDCn8ANmes Message-ID: Subject: Re: [PATCH v3 08/13] mm, swap: use an enum to define all cluster flags and wrap flags changes To: Baoquan He Cc: linux-mm@kvack.org, Andrew Morton , Chris Li , Barry Song , Ryan Roberts , Hugh Dickins , Yosry Ahmed , "Huang, Ying" , Nhat Pham , Johannes Weiner , Kalesh Singh , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9C38D40003 X-Stat-Signature: dqqke8wsah5yt19h7uda41u3xitt68e5 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1736747384-269517 X-HE-Meta: U2FsdGVkX1+h5MU87ccyTkKmHLd5o5iP8kWql0QokETyVCrGQKgm7ivsj8aMfILcuskBdzf6jvQyys+1Z7nILHeGhHG0b5p03S8ADEFNXVslP8d4TfMdjp4NeLmqfLbOBrKcHqlZUn5zXQlPrI12pasnigMa9RT/oNgqVPrfElCi+p1myqE/Se9NyWicZKNMuTbMxehqgr6eH90Kx7ba6bfj9oK1d5aRX4/jTRKjD9wbH/mD5akDAMpFzvcIeK1dJYOkpv/eZ8kVmqDdbjjaCzJCeGCbzzPhw7wyBg6euiQl7BkFDkuQJPcxRbNgN3xaobXLJLNJRPJkXFlX+KSqoSeTsl5vof4DAXZJZ3xSAR92InJ9PiB2QHZsuEc54BLZrbGLvUA4Al6mkWca0icS/XZTx44g+tusPYfXKvtOG5Mq/CyLyqDklMpLUfN6QF+EG4FupN80RNhSqwS4iCKhiIywYhddlBp7l6/xWjfUnajC/jovXeKpzKX0IEgUtFj58lG0N5//9C3J+YjogA/JYwcWF1DkIF1TctTUsNblQK/B3e68vIr4xeii/kJMr34kzyrI1SFRaXHCa5H8AkoQANaQLGVqd2gQu8MBSAnyyTrzm/60m5XF8KOSDuGVw8vs9/AD99nYxyS5v+TKKl8TwYBmJOnMt24x62C5HbPQC+TSr/rtOt1bN9C50FUVQ0cNAmFrI9y2fYobWIZAckn4YOJwdt4HNcLuF9+XIjZiE+D4WGFbyYiqHt/v2cKtXPjTj2OAP4gSfWog4/i9K9OSjOHtFO2wHelCUZPGDbdhJmzw0RceK7UFkuzEaMonluMVwWZAzXAIAcH9ycdZ8BVOnDyPDf8PVOz22sVHo3xpotCRkQ6eGAdmNMOPAZUzxAuY5CEiJwgXx/5jiJ/kndG2+rlVM2TQofcIRhA+jElCbxGZQyYJrUL7NpIGoTjMly1aW4kAp6dwy79uwmsCynN KUwG0gzX axY/w5pDwDiOLbHhZz0JIKR2c7DBqVZ0+oNYih7/gV592PwVEO0KaNB+B9Op5HpSC3j/NIYtUHgD2s48bmecEIRCFKNMEfGYcqLPGJRbYzRr7PqVEuUoIqGci6IGlPSg5091new05HCfmpuzUyKO2xc6k2rc2T4J9SIBDIAwDkkaTnx9JfZexWQuXyVHvNUUsKv1VD6xNaXibMhIQ2HMGXyU1d4tR6KyvkoYvMX5Frw1j8wMZReVZLOt8750sWwkrLXz2VgVS8RURlCpW56pTlk0yZxrGvIKfW5SXj+ONYW8Is3UUjPsXEoPmh7ZBVEtHyNCPs7VlPU6H8/8Ij0as2AL4zvGyE8iRdU+RNNFrF/3TbvwCr5j4WnxyUb/pIQ7keAtadBjOEWCJzQ0= 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 Mon, Jan 6, 2025 at 4:43=E2=80=AFPM Baoquan He wrote: > > On 12/31/24 at 01:46am, Kairui Song wrote: > > From: Kairui Song > > > > Currently, we are only using flags to indicate which list the cluster > > is on. Using one bit for each list type might be a waste, as the list > > type grows, we will consume too many bits. Additionally, the current > > mixed usage of '&' and '=3D=3D' is a bit confusing. > > I think this kind of converting can only happen when the type is > exclusive on each cluster. Then we can set and use > 'ci->flags =3D=3D CLUSTER_FLAG_XXX' to check it. Hi Baoquan, Not sure what you mean. The flags are exclusive, and after this commit, we are always using "ci->flags =3D=3D CLUSTER_FLAG_XXX" to check the flag. > > > > > Make it clean by using an enum to define all possible cluster > > statuses. Only an off-list cluster will have the NONE (0) flag. > > And use a wrapper to annotate and sanitize all flag settings > > and list movements. > > > > Suggested-by: Chris Li > > Signed-off-by: Kairui Song > > --- > > include/linux/swap.h | 17 +++++++--- > > mm/swapfile.c | 75 +++++++++++++++++++++++--------------------- > > 2 files changed, 52 insertions(+), 40 deletions(-) > > > > diff --git a/include/linux/swap.h b/include/linux/swap.h > > index 02120f1005d5..339d7f0192ff 100644 > > --- a/include/linux/swap.h > > +++ b/include/linux/swap.h > > @@ -257,10 +257,19 @@ struct swap_cluster_info { > > u8 order; > > struct list_head list; > > }; > > -#define CLUSTER_FLAG_FREE 1 /* This cluster is free */ > > -#define CLUSTER_FLAG_NONFULL 2 /* This cluster is on nonfull list */ > > -#define CLUSTER_FLAG_FRAG 4 /* This cluster is on nonfull list */ > > -#define CLUSTER_FLAG_FULL 8 /* This cluster is on full list */ > > + > > +/* All on-list cluster must have a non-zero flag. */ > > +enum swap_cluster_flags { > > + CLUSTER_FLAG_NONE =3D 0, /* For temporary off-list cluster */ > > + CLUSTER_FLAG_FREE, > > + CLUSTER_FLAG_NONFULL, > > + CLUSTER_FLAG_FRAG, > > + /* Clusters with flags above are allocatable */ > > + CLUSTER_FLAG_USABLE =3D CLUSTER_FLAG_FRAG, > > + CLUSTER_FLAG_FULL, > > + CLUSTER_FLAG_DISCARD, > > + CLUSTER_FLAG_MAX, > > +}; > > > > /* > > * The first page in the swap file is the swap header, which is always= marked > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 99fd0b0d84a2..7795a3d27273 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -403,7 +403,7 @@ static void discard_swap_cluster(struct swap_info_s= truct *si, > > > > static inline bool cluster_is_free(struct swap_cluster_info *info) > > { > > - return info->flags & CLUSTER_FLAG_FREE; > > + return info->flags =3D=3D CLUSTER_FLAG_FREE; > > } > > > > static inline unsigned int cluster_index(struct swap_info_struct *si, > > @@ -434,6 +434,27 @@ static inline void unlock_cluster(struct swap_clus= ter_info *ci) > > spin_unlock(&ci->lock); > > } > > > > +static void cluster_move(struct swap_info_struct *si, > ~~~~~~~~~~~~ > Maybe rename it to move_cluster() which has the same naming style as > lock_cluster()/unlock_cluster()? This is what we usually do namin if a > function is action acts on objects. Good idea. > > Other than this, this patch looks great to me. > > > + struct swap_cluster_info *ci, struct list_head *= list, > > + enum swap_cluster_flags new_flags) > > +{ > > + VM_WARN_ON(ci->flags =3D=3D new_flags); > > + BUILD_BUG_ON(1 << sizeof(ci->flags) * BITS_PER_BYTE < CLUSTER_FLA= G_MAX); > > + > > + if (ci->flags =3D=3D CLUSTER_FLAG_NONE) { > > + list_add_tail(&ci->list, list); > > + } else { > > + if (ci->flags =3D=3D CLUSTER_FLAG_FRAG) { > > + VM_WARN_ON(!si->frag_cluster_nr[ci->order]); > > + si->frag_cluster_nr[ci->order]--; > > + } > > + list_move_tail(&ci->list, list); > > + } > > + ci->flags =3D new_flags; > > + if (new_flags =3D=3D CLUSTER_FLAG_FRAG) > > + si->frag_cluster_nr[ci->order]++; > > +} > > + > > /* Add a cluster to discard list and schedule it to do discard */ > > static void swap_cluster_schedule_discard(struct swap_info_struct *si, > > struct swap_cluster_info *ci) > > @@ -447,10 +468,8 @@ static void swap_cluster_schedule_discard(struct s= wap_info_struct *si, > > */ > > memset(si->swap_map + idx * SWAPFILE_CLUSTER, > > SWAP_MAP_BAD, SWAPFILE_CLUSTER); > > - > > - VM_BUG_ON(ci->flags & CLUSTER_FLAG_FREE); > > - list_move_tail(&ci->list, &si->discard_clusters); > > - ci->flags =3D 0; > > + VM_BUG_ON(ci->flags =3D=3D CLUSTER_FLAG_FREE); > > + cluster_move(si, ci, &si->discard_clusters, CLUSTER_FLAG_DISCARD)= ; > > schedule_work(&si->discard_work); > > } > > > > @@ -458,12 +477,7 @@ static void __free_cluster(struct swap_info_struct= *si, struct swap_cluster_info > > { > > lockdep_assert_held(&si->lock); > > lockdep_assert_held(&ci->lock); > > - > > - if (ci->flags) > > - list_move_tail(&ci->list, &si->free_clusters); > > - else > > - list_add_tail(&ci->list, &si->free_clusters); > > - ci->flags =3D CLUSTER_FLAG_FREE; > > + cluster_move(si, ci, &si->free_clusters, CLUSTER_FLAG_FREE); > > ci->order =3D 0; > > } > > > > @@ -479,6 +493,8 @@ static void swap_do_scheduled_discard(struct swap_i= nfo_struct *si) > > while (!list_empty(&si->discard_clusters)) { > > ci =3D list_first_entry(&si->discard_clusters, struct swa= p_cluster_info, list); > > list_del(&ci->list); > > + /* Must clear flag when taking a cluster off-list */ > > + ci->flags =3D CLUSTER_FLAG_NONE; > > idx =3D cluster_index(si, ci); > > spin_unlock(&si->lock); > > > > @@ -519,9 +535,6 @@ static void free_cluster(struct swap_info_struct *s= i, struct swap_cluster_info * > > lockdep_assert_held(&si->lock); > > lockdep_assert_held(&ci->lock); > > > > - if (ci->flags & CLUSTER_FLAG_FRAG) > > - si->frag_cluster_nr[ci->order]--; > > - > > /* > > * If the swap is discardable, prepare discard the cluster > > * instead of free it immediately. The cluster will be freed > > @@ -573,13 +586,9 @@ static void dec_cluster_info_page(struct swap_info= _struct *si, > > return; > > } > > > > - if (!(ci->flags & CLUSTER_FLAG_NONFULL)) { > > - VM_BUG_ON(ci->flags & CLUSTER_FLAG_FREE); > > - if (ci->flags & CLUSTER_FLAG_FRAG) > > - si->frag_cluster_nr[ci->order]--; > > - list_move_tail(&ci->list, &si->nonfull_clusters[ci->order= ]); > > - ci->flags =3D CLUSTER_FLAG_NONFULL; > > - } > > + if (ci->flags !=3D CLUSTER_FLAG_NONFULL) > > + cluster_move(si, ci, &si->nonfull_clusters[ci->order], > > + CLUSTER_FLAG_NONFULL); > > } > > > > static bool cluster_reclaim_range(struct swap_info_struct *si, > > @@ -663,11 +672,13 @@ static bool cluster_alloc_range(struct swap_info_= struct *si, struct swap_cluster > > if (!(si->flags & SWP_WRITEOK)) > > return false; > > > > + VM_BUG_ON(ci->flags =3D=3D CLUSTER_FLAG_NONE); > > + VM_BUG_ON(ci->flags > CLUSTER_FLAG_USABLE); > > + > > if (cluster_is_free(ci)) { > > - if (nr_pages < SWAPFILE_CLUSTER) { > > - list_move_tail(&ci->list, &si->nonfull_clusters[o= rder]); > > - ci->flags =3D CLUSTER_FLAG_NONFULL; > > - } > > + if (nr_pages < SWAPFILE_CLUSTER) > > + cluster_move(si, ci, &si->nonfull_clusters[order]= , > > + CLUSTER_FLAG_NONFULL); > > ci->order =3D order; > > } > > > > @@ -675,14 +686,8 @@ static bool cluster_alloc_range(struct swap_info_s= truct *si, struct swap_cluster > > swap_range_alloc(si, nr_pages); > > ci->count +=3D nr_pages; > > > > - if (ci->count =3D=3D SWAPFILE_CLUSTER) { > > - VM_BUG_ON(!(ci->flags & > > - (CLUSTER_FLAG_FREE | CLUSTER_FLAG_NONFULL | CLU= STER_FLAG_FRAG))); > > - if (ci->flags & CLUSTER_FLAG_FRAG) > > - si->frag_cluster_nr[ci->order]--; > > - list_move_tail(&ci->list, &si->full_clusters); > > - ci->flags =3D CLUSTER_FLAG_FULL; > > - } > > + if (ci->count =3D=3D SWAPFILE_CLUSTER) > > + cluster_move(si, ci, &si->full_clusters, CLUSTER_FLAG_FUL= L); > > > > return true; > > } > > @@ -821,9 +826,7 @@ static unsigned long cluster_alloc_swap_entry(struc= t swap_info_struct *si, int o > > while (!list_empty(&si->nonfull_clusters[order])) { > > ci =3D list_first_entry(&si->nonfull_clusters[ord= er], > > struct swap_cluster_info, l= ist); > > - list_move_tail(&ci->list, &si->frag_clusters[orde= r]); > > - ci->flags =3D CLUSTER_FLAG_FRAG; > > - si->frag_cluster_nr[order]++; > > + cluster_move(si, ci, &si->frag_clusters[order], C= LUSTER_FLAG_FRAG); > > offset =3D alloc_swap_scan_cluster(si, cluster_of= fset(si, ci), > > &found, order, u= sage); > > frags++; > > -- > > 2.47.1 > > > > > >