From: Hongzhen Luo <[email protected]>

When creating the EROFS image, users can specify the fingerprint name.
This is to prepare for the upcoming inode page cache share.

Signed-off-by: Hongzhen Luo <[email protected]>
Signed-off-by: Hongbo Li <[email protected]>
---
 fs/erofs/Kconfig    |  9 +++++++++
 fs/erofs/erofs_fs.h |  6 ++++--
 fs/erofs/internal.h |  2 ++
 fs/erofs/super.c    |  5 +++--
 fs/erofs/xattr.c    | 15 +++++++++++++++
 5 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
index d81f3318417d..c88b6d0714a4 100644
--- a/fs/erofs/Kconfig
+++ b/fs/erofs/Kconfig
@@ -194,3 +194,12 @@ config EROFS_FS_PCPU_KTHREAD_HIPRI
          at higher priority.
 
          If unsure, say N.
+
+config EROFS_FS_PAGE_CACHE_SHARE
+       bool "EROFS page cache share support (experimental)"
+       depends on EROFS_FS && EROFS_FS_XATTR && !EROFS_FS_ONDEMAND
+       help
+         This enables page cache sharing among inodes with identical
+         content fingerprints on the same device.
+
+         If unsure, say N.
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 3d5738f80072..9b9fe1abe0b9 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -35,8 +35,9 @@
 #define EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES  0x00000040
 #define EROFS_FEATURE_INCOMPAT_48BIT           0x00000080
 #define EROFS_FEATURE_INCOMPAT_METABOX         0x00000100
+#define EROFS_FEATURE_INCOMPAT_ISHARE_KEY      0x00000200
 #define EROFS_ALL_FEATURE_INCOMPAT             \
-       ((EROFS_FEATURE_INCOMPAT_METABOX << 1) - 1)
+       ((EROFS_FEATURE_INCOMPAT_ISHARE_KEY << 1) - 1)
 
 #define EROFS_SB_EXTSLOT_SIZE  16
 
@@ -83,7 +84,8 @@ struct erofs_super_block {
        __le32 xattr_prefix_start;      /* start of long xattr prefixes */
        __le64 packed_nid;      /* nid of the special packed inode */
        __u8 xattr_filter_reserved; /* reserved for xattr name filter */
-       __u8 reserved[3];
+       __u8 ishare_xattr_prefix_id;    /* indice the ishare key in prefix 
xattr */
+       __u8 reserved[2];
        __le32 build_time;      /* seconds added to epoch for mkfs time */
        __le64 rootnid_8b;      /* (48BIT on) nid of root directory */
        __le64 reserved2;
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 98fe652aea33..3033252211ba 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -134,6 +134,7 @@ struct erofs_sb_info {
        u32 xattr_blkaddr;
        u32 xattr_prefix_start;
        u8 xattr_prefix_count;
+       u8 ishare_xattr_pfx;    /* ishare prefix xattr index */
        struct erofs_xattr_prefix_item *xattr_prefixes;
        unsigned int xattr_filter_reserved;
 #endif
@@ -234,6 +235,7 @@ EROFS_FEATURE_FUNCS(dedupe, incompat, INCOMPAT_DEDUPE)
 EROFS_FEATURE_FUNCS(xattr_prefixes, incompat, INCOMPAT_XATTR_PREFIXES)
 EROFS_FEATURE_FUNCS(48bit, incompat, INCOMPAT_48BIT)
 EROFS_FEATURE_FUNCS(metabox, incompat, INCOMPAT_METABOX)
+EROFS_FEATURE_FUNCS(ishare_key, incompat, INCOMPAT_ISHARE_KEY)
 EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
 EROFS_FEATURE_FUNCS(xattr_filter, compat, COMPAT_XATTR_FILTER)
 EROFS_FEATURE_FUNCS(shared_ea_in_metabox, compat, COMPAT_SHARED_EA_IN_METABOX)
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 0d88c04684b9..80f032cb2cc3 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -298,6 +298,9 @@ static int erofs_read_superblock(struct super_block *sb)
                if (ret)
                        goto out;
        }
+       if (erofs_sb_has_ishare_key(sbi))
+               sbi->ishare_xattr_pfx =
+                       dsb->ishare_xattr_prefix_id & 
EROFS_XATTR_LONG_PREFIX_MASK;
 
        ret = -EINVAL;
        sbi->feature_incompat = le32_to_cpu(dsb->feature_incompat);
@@ -339,7 +342,6 @@ static int erofs_read_superblock(struct super_block *sb)
                        return -EFSCORRUPTED;   /* self-loop detection */
        }
        sbi->inos = le64_to_cpu(dsb->inos);
-
        sbi->epoch = (s64)le64_to_cpu(dsb->epoch);
        sbi->fixed_nsec = le32_to_cpu(dsb->fixed_nsec);
        super_set_uuid(sb, (void *)dsb->uuid, sizeof(dsb->uuid));
@@ -737,7 +739,6 @@ static int erofs_fc_fill_super(struct super_block *sb, 
struct fs_context *fc)
        err = erofs_xattr_prefixes_init(sb);
        if (err)
                return err;
-
        erofs_set_sysfs_name(sb);
        err = erofs_register_sysfs(sb);
        if (err)
diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
index 396536d9a862..6cb76313c14c 100644
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -519,6 +519,21 @@ int erofs_xattr_prefixes_init(struct super_block *sb)
        }
 
        erofs_put_metabuf(&buf);
+       if (!ret && erofs_sb_has_ishare_key(sbi)) {
+               struct erofs_xattr_long_prefix *new_pfx, *pfx =
+                                       pfs[sbi->ishare_xattr_pfx].prefix;
+
+               new_pfx = krealloc(pfx,
+                                  sizeof(struct erofs_xattr_long_prefix) +
+                                  pfs[sbi->ishare_xattr_pfx].infix_len + 1,
+                                  GFP_KERNEL);
+               if (new_pfx) {
+                       new_pfx->infix[pfs[sbi->ishare_xattr_pfx].infix_len] = 
'\0';
+                       pfs[sbi->ishare_xattr_pfx].prefix = new_pfx;
+               } else {
+                       ret = -ENOMEM;
+               }
+       }
        sbi->xattr_prefixes = pfs;
        if (ret)
                erofs_xattr_prefixes_cleanup(sb);
-- 
2.22.0


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