block/fops.c | 1 + fs/adfs/inode.c | 1 + fs/affs/file.c | 3 ++- fs/bfs/file.c | 1 + fs/buffer.c | 17 +++++++++++++++++ fs/exfat/inode.c | 1 + fs/ext2/inode.c | 1 + fs/fat/inode.c | 1 + fs/hpfs/file.c | 1 + fs/isofs/inode.c | 3 ++- fs/jfs/inode.c | 1 + fs/minix/inode.c | 3 ++- fs/nilfs2/inode.c | 1 + fs/nilfs2/mdt.c | 1 + fs/ntfs3/inode.c | 1 + fs/omfs/file.c | 1 + fs/udf/inode.c | 1 + fs/ufs/inode.c | 3 ++- include/linux/buffer_head.h | 2 ++ mm/filemap.c | 4 ++-- 20 files changed, 42 insertions(+), 6 deletions(-)
Currently, filemap_release_folio() falls back to try_to_free_buffers()
when a filesystem's address_space_operations doesn't provide a
release_folio callback. This creates an inconsistent API where some
buffer_head-based filesystems define release_folio while others rely
on the fallback behavior.
Make the release_folio callback mandatory by:
1. Adding block_release_folio() in fs/buffer.c as the default
implementation for buffer_head-based filesystems. This simply
calls try_to_free_buffers().
2. Updating all buffer_head-based filesystems that use
buffer_migrate_folio() to set .release_folio = block_release_folio
in their address_space_operations.
3. Removing the NULL check and try_to_free_buffers() fallback in
filemap_release_folio(). Now it always calls the release_folio
callback when a mapping exists.
With these changes:
- Makes the pattern explicit across all buffer_head filesystems
- Prevents future bugs from missing release_folio implementations
Filesystems updated: adfs, affs, bfs, exfat, ext2, fat, hpfs, isofs,
jfs, minix, nilfs2, ntfs3, omfs, udf, ufs, plus block/fops.c
Filesystems with existing custom implementations (ext4, gfs2, hfs,
hfsplus, jfs metapage, ocfs2) are unchanged.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Deepakkumar Karn <dkarn@redhat.com>
---
block/fops.c | 1 +
fs/adfs/inode.c | 1 +
fs/affs/file.c | 3 ++-
fs/bfs/file.c | 1 +
fs/buffer.c | 17 +++++++++++++++++
fs/exfat/inode.c | 1 +
fs/ext2/inode.c | 1 +
fs/fat/inode.c | 1 +
fs/hpfs/file.c | 1 +
fs/isofs/inode.c | 3 ++-
fs/jfs/inode.c | 1 +
fs/minix/inode.c | 3 ++-
fs/nilfs2/inode.c | 1 +
fs/nilfs2/mdt.c | 1 +
fs/ntfs3/inode.c | 1 +
fs/omfs/file.c | 1 +
fs/udf/inode.c | 1 +
fs/ufs/inode.c | 3 ++-
include/linux/buffer_head.h | 2 ++
mm/filemap.c | 4 ++--
20 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/block/fops.c b/block/fops.c
index 4d32785b31d9..8adccc5fcb34 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -532,6 +532,7 @@ const struct address_space_operations def_blk_aops = {
.write_end = blkdev_write_end,
.migrate_folio = buffer_migrate_folio_norefs,
.is_dirty_writeback = buffer_check_dirty_writeback,
+ .release_folio = block_release_folio,
};
#else /* CONFIG_BUFFER_HEAD */
static int blkdev_read_folio(struct file *file, struct folio *folio)
diff --git a/fs/adfs/inode.c b/fs/adfs/inode.c
index 6830f8bc8d4e..ca7411c40ace 100644
--- a/fs/adfs/inode.c
+++ b/fs/adfs/inode.c
@@ -83,6 +83,7 @@ static const struct address_space_operations adfs_aops = {
.write_end = generic_write_end,
.migrate_folio = buffer_migrate_folio,
.bmap = _adfs_bmap,
+ .release_folio = block_release_folio,
};
/*
diff --git a/fs/affs/file.c b/fs/affs/file.c
index 765c3443663e..c03ac926c3a5 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -464,7 +464,8 @@ const struct address_space_operations affs_aops = {
.write_end = affs_write_end,
.direct_IO = affs_direct_IO,
.migrate_folio = buffer_migrate_folio,
- .bmap = _affs_bmap
+ .bmap = _affs_bmap,
+ .release_folio = block_release_folio,
};
static inline struct buffer_head *
diff --git a/fs/bfs/file.c b/fs/bfs/file.c
index d33d6bde992b..34ab8ad50302 100644
--- a/fs/bfs/file.c
+++ b/fs/bfs/file.c
@@ -198,6 +198,7 @@ const struct address_space_operations bfs_aops = {
.write_end = generic_write_end,
.migrate_folio = buffer_migrate_folio,
.bmap = bfs_bmap,
+ .release_folio = block_release_folio,
};
const struct inode_operations bfs_file_inops;
diff --git a/fs/buffer.c b/fs/buffer.c
index 838c0c571022..eb856901ac3a 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2914,6 +2914,23 @@ drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
return false;
}
+/**
+ * block_release_folio - Release buffers attached to a BH-based filesystems.
+ * @folio: The folio.
+ * @gfp: The gfp parameter.
+ *
+ * This is the default release_folio implementation for buffer_head based
+ * filesystems. Filesystems with special requirements
+ * should implement their own release_folio callback.
+ *
+ * Return: true if buffers were released, false otherwise.
+ */
+bool block_release_folio(struct folio *folio, gfp_t gfp)
+{
+ return try_to_free_buffers(folio);
+}
+EXPORT_SYMBOL(block_release_folio);
+
/**
* try_to_free_buffers - Release buffers attached to this folio.
* @folio: The folio.
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index f9501c3a3666..2586fee189d6 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -567,6 +567,7 @@ static const struct address_space_operations exfat_aops = {
.direct_IO = exfat_direct_IO,
.bmap = exfat_aop_bmap,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
static inline unsigned long exfat_hash(loff_t i_pos)
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index dbfe9098a124..632463a203e4 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -980,6 +980,7 @@ const struct address_space_operations ext2_aops = {
.migrate_folio = buffer_migrate_folio,
.is_partially_uptodate = block_is_partially_uptodate,
.error_remove_folio = generic_error_remove_folio,
+ .release_folio = block_release_folio,
};
static const struct address_space_operations ext2_dax_aops = {
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 0b6009cd1844..b6f13927e75b 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -348,6 +348,7 @@ static const struct address_space_operations fat_aops = {
.direct_IO = fat_direct_IO,
.bmap = _fat_bmap,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
/*
diff --git a/fs/hpfs/file.c b/fs/hpfs/file.c
index 29e876705369..b242439bf52f 100644
--- a/fs/hpfs/file.c
+++ b/fs/hpfs/file.c
@@ -252,6 +252,7 @@ const struct address_space_operations hpfs_aops = {
.write_end = hpfs_write_end,
.bmap = _hpfs_bmap,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
const struct file_operations hpfs_file_ops =
diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index b7cbe126faf3..d79865bc86b3 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -1162,7 +1162,8 @@ static sector_t _isofs_bmap(struct address_space *mapping, sector_t block)
static const struct address_space_operations isofs_aops = {
.read_folio = isofs_read_folio,
.readahead = isofs_readahead,
- .bmap = _isofs_bmap
+ .bmap = _isofs_bmap,
+ .release_folio = block_release_folio,
};
static int isofs_read_level3_size(struct inode *inode)
diff --git a/fs/jfs/inode.c b/fs/jfs/inode.c
index 4709762713ef..f4c9c84fd75a 100644
--- a/fs/jfs/inode.c
+++ b/fs/jfs/inode.c
@@ -364,6 +364,7 @@ const struct address_space_operations jfs_aops = {
.bmap = jfs_bmap,
.direct_IO = jfs_direct_IO,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
/*
diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index 51ea9bdc813f..1d351d01a0c7 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -486,7 +486,8 @@ static const struct address_space_operations minix_aops = {
.write_end = generic_write_end,
.migrate_folio = buffer_migrate_folio,
.bmap = minix_bmap,
- .direct_IO = noop_direct_IO
+ .direct_IO = noop_direct_IO,
+ .release_folio = block_release_folio,
};
static const struct inode_operations minix_symlink_inode_operations = {
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 51bde45d5865..b8263da21038 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -280,6 +280,7 @@ const struct address_space_operations nilfs_aops = {
.direct_IO = nilfs_direct_IO,
.migrate_folio = buffer_migrate_folio_norefs,
.is_partially_uptodate = block_is_partially_uptodate,
+ .release_folio = block_release_folio,
};
const struct address_space_operations nilfs_buffer_cache_aops = {
diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index 946b0d3534a5..bc1c620e2dce 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -443,6 +443,7 @@ static const struct address_space_operations def_mdt_aops = {
.invalidate_folio = block_invalidate_folio,
.writepages = nilfs_mdt_writeback,
.migrate_folio = buffer_migrate_folio_norefs,
+ .release_folio = block_release_folio,
};
static const struct inode_operations def_mdt_iops;
diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
index 0a9ac5efeb67..b671803147b5 100644
--- a/fs/ntfs3/inode.c
+++ b/fs/ntfs3/inode.c
@@ -2102,6 +2102,7 @@ const struct address_space_operations ntfs_aops = {
.dirty_folio = block_dirty_folio,
.migrate_folio = buffer_migrate_folio,
.invalidate_folio = block_invalidate_folio,
+ .release_folio = block_release_folio,
};
const struct address_space_operations ntfs_aops_cmpr = {
diff --git a/fs/omfs/file.c b/fs/omfs/file.c
index 49a1de5a827f..25f88a2f36de 100644
--- a/fs/omfs/file.c
+++ b/fs/omfs/file.c
@@ -376,5 +376,6 @@ const struct address_space_operations omfs_aops = {
.write_end = generic_write_end,
.bmap = omfs_bmap,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 7fae8002344a..5ba17373f9b1 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -335,6 +335,7 @@ const struct address_space_operations udf_aops = {
.direct_IO = udf_direct_IO,
.bmap = udf_bmap,
.migrate_folio = buffer_migrate_folio,
+ .release_folio = block_release_folio,
};
/*
diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c
index e2b0a35de2a7..4eed8f530737 100644
--- a/fs/ufs/inode.c
+++ b/fs/ufs/inode.c
@@ -514,7 +514,8 @@ const struct address_space_operations ufs_aops = {
.write_begin = ufs_write_begin,
.write_end = ufs_write_end,
.migrate_folio = buffer_migrate_folio,
- .bmap = ufs_bmap
+ .bmap = ufs_bmap,
+ .release_folio = block_release_folio,
};
static void ufs_set_inode_ops(struct inode *inode)
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index b16b88bfbc3e..16c793dad6f6 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -515,6 +515,7 @@ bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
void buffer_init(void);
bool try_to_free_buffers(struct folio *folio);
+bool block_release_folio(struct folio *folio, gfp_t gfp);
int inode_has_buffers(struct inode *inode);
void invalidate_inode_buffers(struct inode *inode);
int remove_inode_buffers(struct inode *inode);
@@ -528,6 +529,7 @@ extern int buffer_heads_over_limit;
static inline void buffer_init(void) {}
static inline bool try_to_free_buffers(struct folio *folio) { return true; }
+static inline bool block_release_folio(struct folio *folio, gfp_t gfp) { return true; }
static inline int inode_has_buffers(struct inode *inode) { return 0; }
static inline void invalidate_inode_buffers(struct inode *inode) {}
static inline int remove_inode_buffers(struct inode *inode) { return 1; }
diff --git a/mm/filemap.c b/mm/filemap.c
index ebd75684cb0a..5af38d81498d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -4490,9 +4490,9 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp)
if (folio_test_writeback(folio))
return false;
- if (mapping && mapping->a_ops->release_folio)
+ if (mapping)
return mapping->a_ops->release_folio(folio, gfp);
- return try_to_free_buffers(folio);
+ return true;
}
EXPORT_SYMBOL(filemap_release_folio);
--
2.52.0On Sat 20-12-25 01:07:52, Deepakkumar Karn wrote:
> Currently, filemap_release_folio() falls back to try_to_free_buffers()
> when a filesystem's address_space_operations doesn't provide a
> release_folio callback. This creates an inconsistent API where some
> buffer_head-based filesystems define release_folio while others rely
> on the fallback behavior.
>
> Make the release_folio callback mandatory by:
>
> 1. Adding block_release_folio() in fs/buffer.c as the default
> implementation for buffer_head-based filesystems. This simply
> calls try_to_free_buffers().
>
> 2. Updating all buffer_head-based filesystems that use
> buffer_migrate_folio() to set .release_folio = block_release_folio
> in their address_space_operations.
>
> 3. Removing the NULL check and try_to_free_buffers() fallback in
> filemap_release_folio(). Now it always calls the release_folio
> callback when a mapping exists.
>
> With these changes:
> - Makes the pattern explicit across all buffer_head filesystems
> - Prevents future bugs from missing release_folio implementations
>
> Filesystems updated: adfs, affs, bfs, exfat, ext2, fat, hpfs, isofs,
> jfs, minix, nilfs2, ntfs3, omfs, udf, ufs, plus block/fops.c
>
> Filesystems with existing custom implementations (ext4, gfs2, hfs,
> hfsplus, jfs metapage, ocfs2) are unchanged.
>
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Deepakkumar Karn <dkarn@redhat.com>
...
> diff --git a/fs/affs/file.c b/fs/affs/file.c
> index 765c3443663e..c03ac926c3a5 100644
> --- a/fs/affs/file.c
> +++ b/fs/affs/file.c
> @@ -464,7 +464,8 @@ const struct address_space_operations affs_aops = {
> .write_end = affs_write_end,
> .direct_IO = affs_direct_IO,
> .migrate_folio = buffer_migrate_folio,
> - .bmap = _affs_bmap
> + .bmap = _affs_bmap,
> + .release_folio = block_release_folio,
> };
>
I think affs_aops_ofs need .release_folio as well...
Also befs_aops, ecryptfs_aops, efs_aops, vxfs_aops, hfs_aops, hfsplus_aops,
nilfs_buffer_cache_aops, qnx4_aops, qnx6_aops definitely need .release_folio. ntfs_aops_cmpr
might need it as well - not sure.
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 838c0c571022..eb856901ac3a 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2914,6 +2914,23 @@ drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
> return false;
> }
>
> +/**
> + * block_release_folio - Release buffers attached to a BH-based filesystems.
> + * @folio: The folio.
^^ "The folio with attached buffers."
> + * @gfp: The gfp parameter.
^^ "Memory allocation flags (and I/O mode)."
> + *
> + * This is the default release_folio implementation for buffer_head based
> + * filesystems. Filesystems with special requirements
> + * should implement their own release_folio callback.
> + *
> + * Return: true if buffers were released, false otherwise.
> + */
Otherwise the patch looks good to me.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
On Mon, Dec 22, 2025 at 01:38:51PM +0100, Jan Kara wrote:
> > Filesystems updated: adfs, affs, bfs, exfat, ext2, fat, hpfs, isofs,
> > jfs, minix, nilfs2, ntfs3, omfs, udf, ufs, plus block/fops.c
>
> I think affs_aops_ofs need .release_folio as well...
>
> Also befs_aops, ecryptfs_aops, efs_aops, vxfs_aops, hfs_aops, hfsplus_aops,
> nilfs_buffer_cache_aops, qnx4_aops, qnx6_aops definitely need .release_folio. ntfs_aops_cmpr
> might need it as well - not sure.
If we were using a real programming language, we'd have a class for
BH-based filesystems, inherit from it and override each method. But since
we aren't, let's see what we can do in C ...
#define BH_DEFAULT_AOPS \
.dirty_folio = block_dirty_folio, \
.invalidate_folio = block_invalidate_folio, \
.migrate_folio = buffer_migrate_folio, \
.is_partially_uptodate = block_is_partially_uptodate, \
.error_remove_folio = generic_error_remove_folio,
As I understand C, later initialisers override earlier ones [1].
GCC does have an optional warning (-Woverride-init) which is included in
-W but not -Wall. Some parts of the kernel explicitly turn this off, either
like this:
arch/arm64/kvm/Makefile:CFLAGS_sys_regs.o += -Wno-override-init
or like this:
drivers/gpu/drm/i915/display/intel_display_device.c:__diag_ignore_all("-Woverride-init", "Allow field initialization overrides for display info");
I'd be happy to do either of those for filesystems.
[1] Test program:
struct ops { void (*frob)(void); };
static void my_frob(void) { return; }
void generic_frob(void);
struct ops my_ops = {
.frob = generic_frob,
.frob = my_frob,
};
int main(void)
{
return 0;
}
$ gcc -Wall -o test2 test2.c
links without any missing symbols
On Mon 22-12-25 15:13:26, Matthew Wilcox wrote: > On Mon, Dec 22, 2025 at 01:38:51PM +0100, Jan Kara wrote: > > > Filesystems updated: adfs, affs, bfs, exfat, ext2, fat, hpfs, isofs, > > > jfs, minix, nilfs2, ntfs3, omfs, udf, ufs, plus block/fops.c > > > > I think affs_aops_ofs need .release_folio as well... > > > > Also befs_aops, ecryptfs_aops, efs_aops, vxfs_aops, hfs_aops, hfsplus_aops, > > nilfs_buffer_cache_aops, qnx4_aops, qnx6_aops definitely need .release_folio. ntfs_aops_cmpr > > might need it as well - not sure. > > If we were using a real programming language, we'd have a class for > BH-based filesystems, inherit from it and override each method. But since > we aren't, let's see what we can do in C ... > > #define BH_DEFAULT_AOPS \ > .dirty_folio = block_dirty_folio, \ > .invalidate_folio = block_invalidate_folio, \ > .migrate_folio = buffer_migrate_folio, \ > .is_partially_uptodate = block_is_partially_uptodate, \ > .error_remove_folio = generic_error_remove_folio, > > As I understand C, later initialisers override earlier ones [1]. Frankly, I'm not 100% convinced this will be a win and there is definitely a potential for surprises because filesystems tend to do weird things so this will need to carefully go filesystem by filesystem... So I wouldn't complicate this patch with a change like this. Let's clean up .release_folio first and we can look into cutting boilerplate initializations later. Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
On Mon, Dec 22, 2025 at 9:18 PM Jan Kara <jack@suse.cz> wrote: > > On Mon 22-12-25 15:13:26, Matthew Wilcox wrote: > > On Mon, Dec 22, 2025 at 01:38:51PM +0100, Jan Kara wrote: > > > > Filesystems updated: adfs, affs, bfs, exfat, ext2, fat, hpfs, isofs, > > > > jfs, minix, nilfs2, ntfs3, omfs, udf, ufs, plus block/fops.c > > > > > > I think affs_aops_ofs need .release_folio as well... > > > > > > Also befs_aops, ecryptfs_aops, efs_aops, vxfs_aops, hfs_aops, hfsplus_aops, > > > nilfs_buffer_cache_aops, qnx4_aops, qnx6_aops definitely need .release_folio. ntfs_aops_cmpr > > > might need it as well - not sure. > > > > If we were using a real programming language, we'd have a class for > > BH-based filesystems, inherit from it and override each method. But since > > we aren't, let's see what we can do in C ... > > > > #define BH_DEFAULT_AOPS \ > > .dirty_folio = block_dirty_folio, \ > > .invalidate_folio = block_invalidate_folio, \ > > .migrate_folio = buffer_migrate_folio, \ > > .is_partially_uptodate = block_is_partially_uptodate, \ > > .error_remove_folio = generic_error_remove_folio, > > > > As I understand C, later initialisers override earlier ones [1]. > > Frankly, I'm not 100% convinced this will be a win and there is definitely > a potential for surprises because filesystems tend to do weird things so > this will need to carefully go filesystem by filesystem... So I wouldn't > complicate this patch with a change like this. Let's clean up > .release_folio first and we can look into cutting boilerplate > initializations later. > Thank you Jan and Matthew for the review. @Jan, I will address the feedback for adding release_folio, in missing filesystems. I will check and add it wherever I find it missing/needed. - affs_aops_ofs - befs_aops - ecryptfs_aops - efs_aops - vxfs_aops - hfs_aops - hfsplus_aops - nilfs_buffer_cache_aops - qnx4_aops - qnx6_aops - ntfs_aops_cmpr As there are more changes, and to be honest this being one of my first patches of this scale, I am trying to test it as thoroughly as possible. @Matthew, I see what you were suggesting for the BH_DEFAULT_AOPS macro, it would be nice to have, but let me first try to get all the filesystems that need the .release_folio cleanup first. Once these changes are acceptable I can explore reducing boilerplate suggestions as a follow-up. Thanks, Deepakkumar Karn
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