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Tue, 6 Oct 2026 21:00:00 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , Matthew Wilcox , Namjae Jeon , Marc Dionne , Stefan Metzmacher , Eric Van Hensbergen , Dominique Martinet , Ilya Dryomov , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v13 1/8] mm: Make readahead store folio count in readahead_control Date: Tue, 6 Oct 2026 21:59:37 +0100 Message-ID: <20261006205947.608356-2-dhowells@redhat.com> In-Reply-To: <20261006205947.608356-1-dhowells@redhat.com> References: <20261006205947.608356-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-MFC-PROC-ID: kFtnXnZU6k7kkR_fQ_Q5h1Fb-hJ2DFaA36D0xaAH_AE_1791320408 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: w75w845se3tgcw4iyjcxseaq6593m759 X-Rspamd-Queue-Id: 4EE70180010 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1791320417-651581 X-HE-Meta: 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 yIz9t5rx 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Make readahead store folio count in readahead_control so that the filesystem can know in advance how many folios it needs to keep track of. This is cleared by read_pages() in case it is called from a loop. The count is accessed by the filesystem with readahead_folio_count(). Signed-off-by: David Howells Reviewed-by: Paulo Alcantara (Red Hat) cc: Matthew Wilcox cc: netfs@lists.linux.dev cc: linux-mm@kvack.org cc: linux-fsdevel@vger.kernel.org --- include/linux/pagemap.h | 10 ++++++++++ mm/readahead.c | 5 +++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 0adfa6605653..b7154b81d0d7 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -1411,6 +1411,7 @@ struct readahead_control { struct file_ra_state *ra; /* private: use the readahead_* accessors instead */ pgoff_t _index; + unsigned int _nr_folios; unsigned int _nr_pages; unsigned int _batch_count; bool dropbehind; @@ -1590,6 +1591,15 @@ static inline size_t readahead_batch_length(const struct readahead_control *rac) return rac->_batch_count * PAGE_SIZE; } +/** + * readahead_folio_count - Get the number of folios in this readahead request. + * @rac: The readahead request. + */ +static inline unsigned int readahead_folio_count(const struct readahead_control *rac) +{ + return rac->_nr_folios; +} + static inline unsigned long dir_pages(const struct inode *inode) { return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >> diff --git a/mm/readahead.c b/mm/readahead.c index 6e5563290287..196542fb1c93 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -188,6 +188,7 @@ static void read_pages(struct readahead_control *rac) if (unlikely(rac->_workingset)) psi_memstall_leave(&rac->_pflags); rac->_workingset = false; + rac->_nr_folios = 0; BUG_ON(readahead_count(rac)); } @@ -303,6 +304,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, if (i == mark) folio_set_readahead(folio); ractl->_workingset |= folio_test_workingset(folio); + ractl->_nr_folios++; ractl->_nr_pages += min_nrpages; i += min_nrpages; } @@ -473,6 +475,7 @@ static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index, return err; } + ractl->_nr_folios++; ractl->_nr_pages += 1UL << order; ractl->_workingset |= folio_test_workingset(folio); return 0; @@ -822,6 +825,7 @@ void readahead_expand(struct readahead_control *ractl, ractl->_workingset = true; psi_memstall_enter(&ractl->_pflags); } + ractl->_nr_folios++; ractl->_nr_pages += min_nrpages; ractl->_index = folio->index; } @@ -851,6 +855,7 @@ void readahead_expand(struct readahead_control *ractl, ractl->_workingset = true; psi_memstall_enter(&ractl->_pflags); } + ractl->_nr_folios++; ractl->_nr_pages += min_nrpages; if (ra) { ra->size += min_nrpages;