From: Darrick J. Wong <djwong@xxxxxxxxxx>
Update the ondisk format documentation to discuss the larger maximum
extent counts that were added in 2022.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
.../allocation_groups.asciidoc | 4 +
.../XFS_Filesystem_Structure/ondisk_inode.asciidoc | 61 ++++++++++++++++++--
2 files changed, 58 insertions(+), 7 deletions(-)
diff --git a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
index 7ee5d561..c64b4fad 100644
--- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
+++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
@@ -454,6 +454,10 @@ xref:Timestamps[timestamps] for more information.
The filesystem is not in operable condition, and must be run through
xfs_repair before it can be mounted.
+| +XFS_SB_FEAT_INCOMPAT_NREXT64+ |
+Large file fork extent counts. This greatly expands the maximum number of
+space mappings allowed in data and extended attribute file forks.
+
|=====
*sb_features_log_incompat*::
diff --git a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc
index 1922954e..34c06487 100644
--- a/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc
+++ b/design/XFS_Filesystem_Structure/ondisk_inode.asciidoc
@@ -84,14 +84,41 @@ struct xfs_dinode_core {
__uint32_t di_nlink;
__uint16_t di_projid;
__uint16_t di_projid_hi;
- __uint8_t di_pad[6];
- __uint16_t di_flushiter;
+ union {
+ /* Number of data fork extents if NREXT64 is set */
+ __be64 di_big_nextents;
+
+ /* Padding for V3 inodes without NREXT64 set. */
+ __be64 di_v3_pad;
+
+ /* Padding and inode flush counter for V2 inodes. */
+ struct {
+ __u8 di_v2_pad[6];
+ __be16 di_flushiter;
+ };
+ };
xfs_timestamp_t di_atime;
xfs_timestamp_t di_mtime;
xfs_timestamp_t di_ctime;
xfs_fsize_t di_size;
xfs_rfsblock_t di_nblocks;
xfs_extlen_t di_extsize;
+ union {
+ /*
+ * For V2 inodes and V3 inodes without NREXT64 set, this
+ * is the number of data and attr fork extents.
+ */
+ struct {
+ __be32 di_nextents;
+ __be16 di_anextents;
+ } __packed;
+
+ /* Number of attr fork extents if NREXT64 is set. */
+ struct {
+ __be32 di_big_anextents;
+ __be16 di_nrext64_pad;
+ } __packed;
+ } __packed;
xfs_extnum_t di_nextents;
xfs_aextnum_t di_anextents;
__uint8_t di_forkoff;
@@ -162,7 +189,7 @@ When the number exceeds 65535, the inode is converted to v2 and the link count
is stored in +di_nlink+.
*di_uid*::
-Specifies the owner's UID of the inode.
+Specifies the owner's UID of the inode.
*di_gid*::
Specifies the owner's GID of the inode.
@@ -181,10 +208,17 @@ Specifies the high 16 bits of the owner's project ID in v2 inodes, if the
+XFS_SB_VERSION2_PROJID32BIT+ feature is set; and zero otherwise.
*di_pad[6]*::
-Reserved, must be zero.
+Reserved, must be zero. Only exists for v2 inodes.
*di_flushiter*::
-Incremented on flush.
+Incremented on flush. Only exists for v2 inodes.
+
+*di_v3_pad*::
+Must be zero for v3 inodes without the NREXT64 flag set.
+
+*di_big_nextents*::
+Specifies the number of data extents associated with this inode if the NREXT64
+flag is set. This allows for up to 2^48^ - 1 extent mappings.
*di_atime*::
@@ -231,10 +265,19 @@ file is written to beyond allocated space, XFS will attempt to allocate
additional disk space based on this value.
*di_nextents*::
-Specifies the number of data extents associated with this inode.
+Specifies the number of data extents associated with this inode if the NREXT64
+flag is not set. Supports up to 2^31^ - 1 extents.
*di_anextents*::
-Specifies the number of extended attribute extents associated with this inode.
+Specifies the number of extended attribute extents associated with this inode
+if the NREXT64 flag is not set. Supports up to 2^15^ - 1 extents.
+
+*di_big_anextents*::
+Specifies the number of extended attribute extents associated with this inode
+if the NREXT64 flag is set. Supports up to 2^32^ - 1 extents.
+
+*di_nrext64_pad*::
+Must be zero if the NREXT64 flag is set.
*di_forkoff*::
Specifies the offset into the inode's literal area where the extended attribute
@@ -336,6 +379,10 @@ This inode shares (or has shared) data blocks with another inode.
For files, this is the extent size hint for copy on write operations; see
+di_cowextsize+ for details. For directories, the value in +di_cowextsize+
will be copied to all newly created files and directories.
+| +XFS_DIFLAG2_NREXT64+ |
+Files with this flag set may have up to (2^48^ - 1) extents mapped to the data
+fork and up to (2^32^ - 1) extents mapped to the attribute fork. This flag
+requires the +XFS_SB_FEAT_INCOMPAT_NREXT64+ feature to be enabled.
|=====
*di_cowextsize*::
