Some filesystems like erofs/reiserfs have the ability to pack tail
data into metadata, however iomap framework can only support mapping
inline data with IOMAP_INLINE type, it restricts that:
- inline data should be locating at page #0.
- inline size should equal to .i_size
So we can not use IOMAP_INLINE to handle tail-packing case.
This patch introduces new mapping type IOMAP_TAIL to map tail-packed
data for further use of erofs.
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
fs/iomap.c | 22 ++++++++++++++++++++++
include/linux/iomap.h | 1 +
2 files changed, 23 insertions(+)
diff --git a/fs/iomap.c b/fs/iomap.c
index 12654c2e78f8..ae7777ce77d0 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -280,6 +280,23 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
SetPageUptodate(page);
}
+static void
+iomap_read_tail_data(struct inode *inode, struct page *page,
+ struct iomap *iomap)
+{
+ size_t size = i_size_read(inode) & (PAGE_SIZE - 1);
+ void *addr;
+
+ if (PageUptodate(page))
+ return;
+
+ addr = kmap_atomic(page);
+ memcpy(addr, iomap->inline_data, size);
+ memset(addr + size, 0, PAGE_SIZE - size);
+ kunmap_atomic(addr);
+ SetPageUptodate(page);
+}
+
static loff_t
iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
@@ -298,6 +315,11 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
return PAGE_SIZE;
}
+ if (iomap->type == IOMAP_TAIL) {
+ iomap_read_tail_data(inode, page, iomap);
+ return PAGE_SIZE;
+ }
+
/* zero post-eof blocks as the page may be mapped */
iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
if (plen == 0)
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 2103b94cb1bf..7e1ee48e3db7 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -25,6 +25,7 @@ struct vm_fault;
#define IOMAP_MAPPED 0x03 /* blocks allocated at @addr */
#define IOMAP_UNWRITTEN 0x04 /* blocks allocated at @addr in unwritten state */
#define IOMAP_INLINE 0x05 /* data inline in the inode */
+#define IOMAP_TAIL 0x06 /* tail data packed in metdata */
/*
* Flags for all iomap mappings:
--
2.18.0.rc1
