Modify the writepage handler to find and convert pending delalloc
extents to real allocations. Furthermore, when we're doing non-cow
writes to a part of a file that already has a CoW reservation (the
cowextsz hint that we set up in a subsequent patch facilitates this),
promote the write to copy-on-write so that the entire extent can get
written out as a single extent on disk, thereby reducing post-CoW
fragmentation.
Christoph moved the CoW support code in _map_blocks to a separate helper
function, refactored other functions, and reduced the number of CoW fork
lookups, so I merged those changes here to reduce churn.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/xfs_aops.c | 106 ++++++++++++++++++++++++++++++++++++++++----------
fs/xfs/xfs_aops.h | 4 +-
fs/xfs/xfs_reflink.c | 86 +++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_reflink.h | 4 ++
4 files changed, 178 insertions(+), 22 deletions(-)
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 007a520..7b1e9de 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -31,6 +31,7 @@
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
+#include "xfs_reflink.h"
#include <linux/gfp.h>
#include <linux/mpage.h>
#include <linux/pagevec.h>
@@ -341,6 +342,7 @@ xfs_map_blocks(
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
+ ASSERT(type != XFS_IO_COW);
if (type == XFS_IO_UNWRITTEN)
bmapi_flags |= XFS_BMAPI_IGSTATE;
@@ -355,6 +357,13 @@ xfs_map_blocks(
offset_fsb = XFS_B_TO_FSBT(mp, offset);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
imap, &nimaps, bmapi_flags);
+ /*
+ * Truncate an overwrite extent if there's a pending CoW
+ * reservation before the end of this extent. This forces us
+ * to come back to writepage to take care of the CoW.
+ */
+ if (nimaps && type == XFS_IO_OVERWRITE)
+ xfs_reflink_trim_irec_to_next_cow(ip, offset_fsb, imap);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
if (error)
@@ -365,8 +374,7 @@ xfs_map_blocks(
error = xfs_iomap_write_allocate(ip, XFS_DATA_FORK, offset,
imap);
if (!error)
- trace_xfs_map_blocks_alloc(ip, offset, count, type,
- imap);
+ trace_xfs_map_blocks_alloc(ip, offset, count, type, imap);
return error;
}
@@ -645,13 +653,16 @@ xfs_check_page_type(
bh = head = page_buffers(page);
do {
if (buffer_unwritten(bh)) {
- if (type == XFS_IO_UNWRITTEN)
+ if (type == XFS_IO_UNWRITTEN ||
+ type == XFS_IO_COW)
return true;
} else if (buffer_delay(bh)) {
- if (type == XFS_IO_DELALLOC)
+ if (type == XFS_IO_DELALLOC ||
+ type == XFS_IO_COW)
return true;
} else if (buffer_dirty(bh) && buffer_mapped(bh)) {
- if (type == XFS_IO_OVERWRITE)
+ if (type == XFS_IO_OVERWRITE ||
+ type == XFS_IO_COW)
return true;
}
@@ -739,6 +750,56 @@ xfs_aops_discard_page(
return;
}
+static int
+xfs_map_cow(
+ struct xfs_writepage_ctx *wpc,
+ struct inode *inode,
+ loff_t offset,
+ unsigned int *new_type)
+{
+ struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_bmbt_irec imap;
+ bool is_cow = false, need_alloc = false;
+ int error;
+
+ /*
+ * If we already have a valid COW mapping keep using it.
+ */
+ if (wpc->io_type == XFS_IO_COW) {
+ wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, offset);
+ if (wpc->imap_valid) {
+ *new_type = XFS_IO_COW;
+ return 0;
+ }
+ }
+
+ /*
+ * Else we need to check if there is a COW mapping at this offset.
+ */
+ xfs_ilock(ip, XFS_ILOCK_SHARED);
+ is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap, &need_alloc);
+ xfs_iunlock(ip, XFS_ILOCK_SHARED);
+
+ if (!is_cow)
+ return 0;
+
+ /*
+ * And if the COW mapping has a delayed extent here we need to
+ * allocate real space for it now.
+ */
+ if (need_alloc) {
+ error = xfs_iomap_write_allocate(ip, XFS_COW_FORK, offset,
+ &imap);
+ if (error)
+ return error;
+ }
+
+ wpc->io_type = *new_type = XFS_IO_COW;
+ wpc->imap_valid = true;
+ wpc->imap = imap;
+ return 0;
+}
+
/*
* We implement an immediate ioend submission policy here to avoid needing to
* chain multiple ioends and hence nest mempool allocations which can violate
@@ -771,6 +832,7 @@ xfs_writepage_map(
int error = 0;
int count = 0;
int uptodate = 1;
+ unsigned int new_type;
bh = head = page_buffers(page);
offset = page_offset(page);
@@ -791,22 +853,13 @@ xfs_writepage_map(
continue;
}
- if (buffer_unwritten(bh)) {
- if (wpc->io_type != XFS_IO_UNWRITTEN) {
- wpc->io_type = XFS_IO_UNWRITTEN;
- wpc->imap_valid = false;
- }
- } else if (buffer_delay(bh)) {
- if (wpc->io_type != XFS_IO_DELALLOC) {
- wpc->io_type = XFS_IO_DELALLOC;
- wpc->imap_valid = false;
- }
- } else if (buffer_uptodate(bh)) {
- if (wpc->io_type != XFS_IO_OVERWRITE) {
- wpc->io_type = XFS_IO_OVERWRITE;
- wpc->imap_valid = false;
- }
- } else {
+ if (buffer_unwritten(bh))
+ new_type = XFS_IO_UNWRITTEN;
+ else if (buffer_delay(bh))
+ new_type = XFS_IO_DELALLOC;
+ else if (buffer_uptodate(bh))
+ new_type = XFS_IO_OVERWRITE;
+ else {
if (PageUptodate(page))
ASSERT(buffer_mapped(bh));
/*
@@ -819,6 +872,17 @@ xfs_writepage_map(
continue;
}
+ if (xfs_is_reflink_inode(XFS_I(inode))) {
+ error = xfs_map_cow(wpc, inode, offset, &new_type);
+ if (error)
+ goto out;
+ }
+
+ if (wpc->io_type != new_type) {
+ wpc->io_type = new_type;
+ wpc->imap_valid = false;
+ }
+
if (wpc->imap_valid)
wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap,
offset);
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index 1950e3b..b3c6634 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -28,13 +28,15 @@ enum {
XFS_IO_DELALLOC, /* covers delalloc region */
XFS_IO_UNWRITTEN, /* covers allocated but uninitialized data */
XFS_IO_OVERWRITE, /* covers already allocated extent */
+ XFS_IO_COW, /* covers copy-on-write extent */
};
#define XFS_IO_TYPES \
{ XFS_IO_INVALID, "invalid" }, \
{ XFS_IO_DELALLOC, "delalloc" }, \
{ XFS_IO_UNWRITTEN, "unwritten" }, \
- { XFS_IO_OVERWRITE, "overwrite" }
+ { XFS_IO_OVERWRITE, "overwrite" }, \
+ { XFS_IO_COW, "CoW" }
/*
* Structure for buffered I/O completions.
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 05a7fe6..e8c7c85 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -314,3 +314,89 @@ xfs_reflink_reserve_cow_range(
return error;
}
+
+/*
+ * Find the CoW reservation (and whether or not it needs block allocation)
+ * for a given byte offset of a file.
+ */
+bool
+xfs_reflink_find_cow_mapping(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ struct xfs_bmbt_irec *imap,
+ bool *need_alloc)
+{
+ struct xfs_bmbt_irec irec;
+ struct xfs_ifork *ifp;
+ struct xfs_bmbt_rec_host *gotp;
+ xfs_fileoff_t bno;
+ xfs_extnum_t idx;
+
+ ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
+
+ if (!xfs_is_reflink_inode(ip))
+ return false;
+
+ /* Find the extent in the CoW fork. */
+ ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+ bno = XFS_B_TO_FSBT(ip->i_mount, offset);
+ gotp = xfs_iext_bno_to_ext(ifp, bno, &idx);
+ if (!gotp)
+ return false;
+
+ xfs_bmbt_get_all(gotp, &irec);
+ if (bno >= irec.br_startoff + irec.br_blockcount ||
+ bno < irec.br_startoff)
+ return false;
+
+ trace_xfs_reflink_find_cow_mapping(ip, offset, 1, XFS_IO_OVERWRITE,
+ &irec);
+
+ /* If it's still delalloc, we must allocate later. */
+ *imap = irec;
+ *need_alloc = !!(isnullstartblock(irec.br_startblock));
+
+ return true;
+}
+
+/*
+ * Trim an extent to end at the next CoW reservation past offset_fsb.
+ */
+int
+xfs_reflink_trim_irec_to_next_cow(
+ struct xfs_inode *ip,
+ xfs_fileoff_t offset_fsb,
+ struct xfs_bmbt_irec *imap)
+{
+ struct xfs_bmbt_irec irec;
+ struct xfs_ifork *ifp;
+ struct xfs_bmbt_rec_host *gotp;
+ xfs_extnum_t idx;
+
+ if (!xfs_is_reflink_inode(ip))
+ return 0;
+
+ /* Find the extent in the CoW fork. */
+ ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+ gotp = xfs_iext_bno_to_ext(ifp, offset_fsb, &idx);
+ if (!gotp)
+ return 0;
+ xfs_bmbt_get_all(gotp, &irec);
+
+ /* This is the extent before; try sliding up one. */
+ if (irec.br_startoff < offset_fsb) {
+ idx++;
+ if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
+ return 0;
+ gotp = xfs_iext_get_ext(ifp, idx);
+ xfs_bmbt_get_all(gotp, &irec);
+ }
+
+ if (irec.br_startoff >= imap->br_startoff + imap->br_blockcount)
+ return 0;
+
+ imap->br_blockcount = irec.br_startoff - imap->br_startoff;
+ trace_xfs_reflink_trim_irec(ip, imap);
+
+ return 0;
+}
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index f824f87..11408c0 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -28,5 +28,9 @@ extern int xfs_reflink_trim_around_shared(struct xfs_inode *ip,
extern int xfs_reflink_reserve_cow_range(struct xfs_inode *ip,
xfs_off_t offset, xfs_off_t count);
+extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
+ struct xfs_bmbt_irec *imap, bool *need_alloc);
+extern int xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
+ xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap);
#endif /* __XFS_REFLINK_H */
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