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iomap: share iomap_unshare_iter predicate code with fsdax

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The predicate code that iomap_unshare_iter uses to decide if it's really
needs to unshare a file range mapping should be shared with the fsdax
version, because right now they're opencoded and inconsistent.

Note that we simplify the predicate logic a bit -- we no longer allow
unsharing of inline data mappings, but there aren't any filesystems that
allow shared inline data currently.

This is a fix in the sense that it should have been ported to fsdax.

Fixes: b53fdb215d ("iomap: improve shared block detection in iomap_unshare_iter")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/172796813294.1131942.15762084021076932620.stgit@frogsfrogsfrogs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Darrick J. Wong 2024-10-03 08:09:16 -07:00 committed by Christian Brauner
parent b8c4076db5
commit 6ef6a0e821
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GPG Key ID: 91C61BC06578DCA2
3 changed files with 18 additions and 16 deletions
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3
fs/dax.c
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@ -1268,8 +1268,7 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
s64 ret = 0;
void *daddr = NULL, *saddr = NULL;
/* don't bother with blocks that are not shared to start with */
if (!(iomap->flags & IOMAP_F_SHARED))
if (!iomap_want_unshare_iter(iter))
return length;
id = dax_read_lock();

30
fs/iomap/buffered-io.c
View File

@ -1309,19 +1309,12 @@ void iomap_file_buffered_write_punch_delalloc(struct inode *inode,
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write_punch_delalloc);
static loff_t iomap_unshare_iter(struct iomap_iter *iter)
bool iomap_want_unshare_iter(const struct iomap_iter *iter)
{
struct iomap *iomap = &iter->iomap;
loff_t pos = iter->pos;
loff_t length = iomap_length(iter);
loff_t written = 0;
/* Don't bother with blocks that are not shared to start with. */
if (!(iomap->flags & IOMAP_F_SHARED))
return length;
/*
* Don't bother with delalloc reservations, holes or unwritten extents.
* Don't bother with blocks that are not shared to start with; or
* mappings that cannot be shared, such as inline data, delalloc
* reservations, holes or unwritten extents.
*
* Note that we use srcmap directly instead of iomap_iter_srcmap as
* unsharing requires providing a separate source map, and the presence
@ -1329,9 +1322,18 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
* IOMAP_F_SHARED which can be set for any data that goes into the COW
* fork for XFS.
*/
if (iter->srcmap.type == IOMAP_HOLE ||
iter->srcmap.type == IOMAP_DELALLOC ||
iter->srcmap.type == IOMAP_UNWRITTEN)
return (iter->iomap.flags & IOMAP_F_SHARED) &&
iter->srcmap.type == IOMAP_MAPPED;
}
static loff_t iomap_unshare_iter(struct iomap_iter *iter)
{
struct iomap *iomap = &iter->iomap;
loff_t pos = iter->pos;
loff_t length = iomap_length(iter);
loff_t written = 0;
if (!iomap_want_unshare_iter(iter))
return length;
do {

1
include/linux/iomap.h
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@ -267,6 +267,7 @@ void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio);
int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
const struct iomap_ops *ops);
bool iomap_want_unshare_iter(const struct iomap_iter *iter);
int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
bool *did_zero, const struct iomap_ops *ops);
int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,