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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jun 2025 07:16:56.7261 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 988a1217-a9f0-490b-69ba-08ddae381c09 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AMS0EPF000001AE.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU0PR08MB8930 X-Stat-Signature: w5duz57bsnis9hjpxjsf8afn6jarbxd3 X-Rspamd-Queue-Id: 7577A2000B X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1750231023-256370 X-HE-Meta: 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 NMdjZ01F 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 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 18/06/25 12:05 am, Kairui Song wrote: > From: Kairui Song > > Currently shmem calls xa_get_order to get the swap radix entry order, > requiring a full tree walk. This can be easily combined with the swap > entry value checking (shmem_confirm_swap) to avoid the duplicated > lookup, which should improve the performance. Nice spot! > > Signed-off-by: Kairui Song > --- > mm/shmem.c | 33 ++++++++++++++++++++++++--------- > 1 file changed, 24 insertions(+), 9 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 4e7ef343a29b..0ad49e57f736 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -505,15 +505,27 @@ static int shmem_replace_entry(struct address_space *mapping, > > /* > * Sometimes, before we decide whether to proceed or to fail, we must check > - * that an entry was not already brought back from swap by a racing thread. > + * that an entry was not already brought back or split by a racing thread. > * > * Checking folio is not enough: by the time a swapcache folio is locked, it > * might be reused, and again be swapcache, using the same swap as before. > + * Returns the swap entry's order if it still presents, else returns -1. > */ > -static bool shmem_confirm_swap(struct address_space *mapping, > - pgoff_t index, swp_entry_t swap) > +static int shmem_swap_check_entry(struct address_space *mapping, pgoff_t index, > + swp_entry_t swap) I think the function name shmem_confirm_swap is already good enough? Anyhow the changed name should at least be shmem_check_entry_is_swap. > { > - return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap); > + XA_STATE(xas, &mapping->i_pages, index); > + int ret = -1; > + void *entry; > + > + rcu_read_lock(); > + do { > + entry = xas_load(&xas); > + if (entry == swp_to_radix_entry(swap)) > + ret = xas_get_order(&xas); > + } while (xas_retry(&xas, entry)); > + rcu_read_unlock(); > + return ret; > } > > /* > @@ -2256,16 +2268,20 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, > return -EIO; > > si = get_swap_device(swap); > - if (!si) { > - if (!shmem_confirm_swap(mapping, index, swap)) > + order = shmem_swap_check_entry(mapping, index, swap); > + if (unlikely(!si)) { > + if (order < 0) > return -EEXIST; > else > return -EINVAL; > } > + if (unlikely(order < 0)) { > + put_swap_device(si); > + return -EEXIST; > + } > > /* Look it up and read it in.. */ > folio = swap_cache_get_folio(swap, NULL, 0); > - order = xa_get_order(&mapping->i_pages, index); > if (!folio) { > int nr_pages = 1 << order; > bool fallback_order0 = false; > @@ -2415,7 +2431,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, > *foliop = folio; > return 0; > failed: > - if (!shmem_confirm_swap(mapping, index, swap)) > + if (shmem_swap_check_entry(mapping, index, swap) < 0) > error = -EEXIST; > if (error == -EIO) > shmem_set_folio_swapin_error(inode, index, folio, swap, > @@ -2428,7 +2444,6 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, > folio_put(folio); > } > put_swap_device(si); > - > return error; > } >