6.1-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit 0201ebf274a306a6ebb95e5dc2d6a0a27c737cac ]
Patch series "mm, netfs, fscache: Stop read optimisation when folio removed from pagecache", v7.
This fixes an optimisation in fscache whereby we don't read from the cache for a particular file until we know that there's data there that we don't have in the pagecache. The problem is that I'm no longer using PG_fscache (aka PG_private_2) to indicate that the page is cached and so I don't get a notification when a cached page is dropped from the pagecache.
The first patch merges some folio_has_private() and filemap_release_folio() pairs and introduces a helper, folio_needs_release(), to indicate if a release is required.
The second patch is the actual fix. Following Willy's suggestions[1], it adds an AS_RELEASE_ALWAYS flag to an address_space that will make filemap_release_folio() always call ->release_folio(), even if PG_private/PG_private_2 aren't set. folio_needs_release() is altered to add a check for this.
This patch (of 2):
Make filemap_release_folio() check folio_has_private(). Then, in most cases, where a call to folio_has_private() is immediately followed by a call to filemap_release_folio(), we can get rid of the test in the pair.
There are a couple of sites in mm/vscan.c that this can't so easily be done. In shrink_folio_list(), there are actually three cases (something different is done for incompletely invalidated buffers), but filemap_release_folio() elides two of them.
In shrink_active_list(), we don't have have the folio lock yet, so the check allows us to avoid locking the page unnecessarily.
A wrapper function to check if a folio needs release is provided for those places that still need to do it in the mm/ directory. This will acquire additional parts to the condition in a future patch.
After this, the only remaining caller of folio_has_private() outside of mm/ is a check in fuse.
Link: https://lkml.kernel.org/r/20230628104852.3391651-1-dhowells@redhat.com Link: https://lkml.kernel.org/r/20230628104852.3391651-2-dhowells@redhat.com Reported-by: Rohith Surabattula rohiths.msft@gmail.com Suggested-by: Matthew Wilcox willy@infradead.org Signed-off-by: David Howells dhowells@redhat.com Cc: Matthew Wilcox willy@infradead.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Steve French sfrench@samba.org Cc: Shyam Prasad N nspmangalore@gmail.com Cc: Rohith Surabattula rohiths.msft@gmail.com Cc: Dave Wysochanski dwysocha@redhat.com Cc: Dominique Martinet asmadeus@codewreck.org Cc: Ilya Dryomov idryomov@gmail.com Cc: "Theodore Ts'o" tytso@mit.edu Cc: Andreas Dilger adilger.kernel@dilger.ca Cc: Xiubo Li xiubli@redhat.com Cc: Jingbo Xu jefflexu@linux.alibaba.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 1898efcdbed3 ("block: update the stable_writes flag in bdev_add") Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/move_extent.c | 12 ++++-------- fs/splice.c | 3 +-- mm/filemap.c | 2 ++ mm/huge_memory.c | 3 +-- mm/internal.h | 8 ++++++++ mm/khugepaged.c | 3 +-- mm/memory-failure.c | 8 +++----- mm/migrate.c | 3 +-- mm/truncate.c | 6 ++---- mm/vmscan.c | 8 ++++---- 10 files changed, 27 insertions(+), 29 deletions(-)
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c index 8dbb87edf24c4..dedc9d445f243 100644 --- a/fs/ext4/move_extent.c +++ b/fs/ext4/move_extent.c @@ -339,10 +339,8 @@ move_extent_per_page(struct file *o_filp, struct inode *donor_inode, ext4_double_up_write_data_sem(orig_inode, donor_inode); goto data_copy; } - if ((folio_has_private(folio[0]) && - !filemap_release_folio(folio[0], 0)) || - (folio_has_private(folio[1]) && - !filemap_release_folio(folio[1], 0))) { + if (!filemap_release_folio(folio[0], 0) || + !filemap_release_folio(folio[1], 0)) { *err = -EBUSY; goto drop_data_sem; } @@ -361,10 +359,8 @@ move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
/* At this point all buffers in range are uptodate, old mapping layout * is no longer required, try to drop it now. */ - if ((folio_has_private(folio[0]) && - !filemap_release_folio(folio[0], 0)) || - (folio_has_private(folio[1]) && - !filemap_release_folio(folio[1], 0))) { + if (!filemap_release_folio(folio[0], 0) || + !filemap_release_folio(folio[1], 0)) { *err = -EBUSY; goto unlock_folios; } diff --git a/fs/splice.c b/fs/splice.c index c4ae54deac42c..d0230cf8ec571 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -65,8 +65,7 @@ static bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe, */ folio_wait_writeback(folio);
- if (folio_has_private(folio) && - !filemap_release_folio(folio, GFP_KERNEL)) + if (!filemap_release_folio(folio, GFP_KERNEL)) goto out_unlock;
/* diff --git a/mm/filemap.c b/mm/filemap.c index 10fe6430693bd..2809b1174f04e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -4005,6 +4005,8 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp) struct address_space * const mapping = folio->mapping;
BUG_ON(!folio_test_locked(folio)); + if (!folio_needs_release(folio)) + return true; if (folio_test_writeback(folio)) return false;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2753fb54cdf38..59577946735b1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2694,8 +2694,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) gfp = current_gfp_context(mapping_gfp_mask(mapping) & GFP_RECLAIM_MASK);
- if (folio_test_private(folio) && - !filemap_release_folio(folio, gfp)) { + if (!filemap_release_folio(folio, gfp)) { ret = -EBUSY; goto out; } diff --git a/mm/internal.h b/mm/internal.h index 6b7ef495b56d3..1fefb5181ab78 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -163,6 +163,14 @@ static inline void set_page_refcounted(struct page *page) set_page_count(page, 1); }
+/* + * Return true if a folio needs ->release_folio() calling upon it. + */ +static inline bool folio_needs_release(struct folio *folio) +{ + return folio_has_private(folio); +} + extern unsigned long highest_memmap_pfn;
/* diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 6fc7db587c453..65bd0b105266a 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1955,8 +1955,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, goto out_unlock; }
- if (folio_has_private(folio) && - !filemap_release_folio(folio, GFP_KERNEL)) { + if (!filemap_release_folio(folio, GFP_KERNEL)) { result = SCAN_PAGE_HAS_PRIVATE; folio_putback_lru(folio); goto out_unlock; diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 6355166a6bb28..5b846ed5dcbe9 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -830,14 +830,12 @@ static int truncate_error_page(struct page *p, unsigned long pfn, struct folio *folio = page_folio(p); int err = mapping->a_ops->error_remove_page(mapping, p);
- if (err != 0) { + if (err != 0) pr_info("%#lx: Failed to punch page: %d\n", pfn, err); - } else if (folio_has_private(folio) && - !filemap_release_folio(folio, GFP_NOIO)) { + else if (!filemap_release_folio(folio, GFP_NOIO)) pr_info("%#lx: failed to release buffers\n", pfn); - } else { + else ret = MF_RECOVERED; - } } else { /* * If the file system doesn't support it just invalidate diff --git a/mm/migrate.c b/mm/migrate.c index 91bd69c61148e..c93dd6a31c31a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -914,8 +914,7 @@ static int fallback_migrate_folio(struct address_space *mapping, * Buffers may be managed in a filesystem specific way. * We must have no buffers or drop them. */ - if (folio_test_private(src) && - !filemap_release_folio(src, GFP_KERNEL)) + if (!filemap_release_folio(src, GFP_KERNEL)) return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_folio(mapping, dst, src, mode); diff --git a/mm/truncate.c b/mm/truncate.c index c0be77e5c0083..0d4dd233f5187 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -19,7 +19,6 @@ #include <linux/highmem.h> #include <linux/pagevec.h> #include <linux/task_io_accounting_ops.h> -#include <linux/buffer_head.h> /* grr. try_to_release_page */ #include <linux/shmem_fs.h> #include <linux/rmap.h> #include "internal.h" @@ -276,7 +275,7 @@ static long mapping_evict_folio(struct address_space *mapping, if (folio_ref_count(folio) > folio_nr_pages(folio) + folio_has_private(folio) + 1) return 0; - if (folio_has_private(folio) && !filemap_release_folio(folio, 0)) + if (!filemap_release_folio(folio, 0)) return 0;
return remove_mapping(mapping, folio); @@ -581,8 +580,7 @@ static int invalidate_complete_folio2(struct address_space *mapping, if (folio->mapping != mapping) return 0;
- if (folio_has_private(folio) && - !filemap_release_folio(folio, GFP_KERNEL)) + if (!filemap_release_folio(folio, GFP_KERNEL)) return 0;
spin_lock(&mapping->host->i_lock); diff --git a/mm/vmscan.c b/mm/vmscan.c index 3f090faa6377f..9f3cfb7caa48d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1992,7 +1992,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, * (refcount == 1) it can be freed. Otherwise, leave * the folio on the LRU so it is swappable. */ - if (folio_has_private(folio)) { + if (folio_needs_release(folio)) { if (!filemap_release_folio(folio, sc->gfp_mask)) goto activate_locked; if (!mapping && folio_ref_count(folio) == 1) { @@ -2618,9 +2618,9 @@ static void shrink_active_list(unsigned long nr_to_scan, }
if (unlikely(buffer_heads_over_limit)) { - if (folio_test_private(folio) && folio_trylock(folio)) { - if (folio_test_private(folio)) - filemap_release_folio(folio, 0); + if (folio_needs_release(folio) && + folio_trylock(folio)) { + filemap_release_folio(folio, 0); folio_unlock(folio); } }