[PATCH 1/7] xfs: enable discarding of folios backing an xfile

Darrick J. Wong
2024-03-27T02:01:27Z

Create a new xfile function to discard the page cache that's backing
part of an xfile. The next patch wil use this to drop parts of an xfile
that aren't needed anymore.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/scrub/trace.h | 1 +
fs/xfs/scrub/xfile.c | 12 ++++++++++++
fs/xfs/scrub/xfile.h | 1 +
3 files changed, 14 insertions(+)

diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 5edbabacc31a8..b5fe49a6da534 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -948,6 +948,7 @@ DEFINE_XFILE_EVENT(xfile_store);
DEFINE_XFILE_EVENT(xfile_seek_data);
DEFINE_XFILE_EVENT(xfile_get_folio);
DEFINE_XFILE_EVENT(xfile_put_folio);
+DEFINE_XFILE_EVENT(xfile_discard);

TRACE_EVENT(xfarray_create,
TP_PROTO(struct xfarray *xfa, unsigned long long required_capacity),
diff --git a/fs/xfs/scrub/xfile.c b/fs/xfs/scrub/xfile.c
index 8cdd863db5850..4e254a0ba0036 100644
--- a/fs/xfs/scrub/xfile.c
+++ b/fs/xfs/scrub/xfile.c
@@ -310,3 +310,15 @@ xfile_put_folio(
folio_unlock(folio);
folio_put(folio);
}
+
+/* Discard the page cache that's backing a range of the xfile. */
+void
+xfile_discard(
+ struct xfile *xf,
+ loff_t pos,
+ u64 count)
+{
+ trace_xfile_discard(xf, pos, count);
+
+ shmem_truncate_range(file_inode(xf->file), pos, pos + count - 1);
+}
diff --git a/fs/xfs/scrub/xfile.h b/fs/xfs/scrub/xfile.h
index 76d78dba7e347..8dfbae1fe33a5 100644
--- a/fs/xfs/scrub/xfile.h
+++ b/fs/xfs/scrub/xfile.h
@@ -17,6 +17,7 @@ int xfile_load(struct xfile *xf, void *buf, size_t count, loff_t pos);
int xfile_store(struct xfile *xf, const void *buf, size_t count,
loff_t pos);

+void xfile_discard(struct xfile *xf, loff_t pos, u64 count);
loff_t xfile_seek_data(struct xfile *xf, loff_t pos);

#define XFILE_MAX_FOLIO_SIZE (PAGE_SIZE << MAX_PAGECACHE_ORDER)