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jffs2: implement mount option parsing and compression overriding

PATCH In review Andres Salomon 2 participants 2 messages Oct 17, 2011 – Oct 19, 2011

Subsystems (3)
VFS Memory technology devices (MTD) Journalling flash file system V2 (JFFS2)
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Andres Salomon

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PATCH v2 1/2 jffs2: implement mount option parsing and compression overriding

Currently jffs2 has compile-time constants (and .config options) controlling whether or not the various compression/decompression drivers are built in and enabled. This is fine for embedded systems, but it clashes with distribution kernels. Distro kernels tend to turn on everything; this causes OpenFirmware to fall over, as it understands ZLIB-compressed inodes. Booting a kernel that has LZO compression enabled, writing to the boot partition, and then rebooting causes OFW to fail to read the kernel from the filesystem. This is because LZO compression has priority when writing new data to jffs2, if LZO is enabled.

This patch adds mount option parsing, and a single supported option ("compr=none"). This adds the flexibility of being able to specify which compressor overrides on a per-superblock basis. For now, we can simply disable compression; additional flexibility coming soon.

v2: kill some printks, and implement show_options as suggested by Artem Bityutskiy.

Signed-off-by Andres Salomon <[email protected]>
---
 fs/jffs2/compr.c       |    9 +++-
 fs/jffs2/fs.c          |    2 +-
 fs/jffs2/jffs2_fs_sb.h |    6 +++
 fs/jffs2/os-linux.h    |    2 +-
 fs/jffs2/super.c       |   97 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 112 insertions(+), 4 deletions(-)
fs/jffs2/compr.c +7 -2
index de42470..97bc74d 100644
@@ -76,13 +76,18 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
 			uint32_t *datalen, uint32_t *cdatalen)
 {
 	int ret = JFFS2_COMPR_NONE;
-	int compr_ret;
+	int mode, compr_ret;
 	struct jffs2_compressor *this, *best=NULL;
 	unsigned char *output_buf = NULL, *tmp_buf;
 	uint32_t orig_slen, orig_dlen;
 	uint32_t best_slen=0, best_dlen=0;
 
-	switch (jffs2_compression_mode) {
+	if (c->mount_opts.override_compr)
+		mode = c->mount_opts.compr;
+	else
+		mode = jffs2_compression_mode;
+
+	switch (mode) {
 	case JFFS2_COMPR_MODE_NONE:
 		break;
 	case JFFS2_COMPR_MODE_PRIORITY:
fs/jffs2/fs.c +1 -1
index bbcb975..5d54b4e 100644
@@ -379,7 +379,7 @@ void jffs2_dirty_inode(struct inode *inode, int flags)
 	jffs2_do_setattr(inode, &iattr);
 }
 
-int jffs2_remount_fs (struct super_block *sb, int *flags, char *data)
+int jffs2_do_remount_fs(struct super_block *sb, int *flags, char *data)
 {
 	struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
fs/jffs2/jffs2_fs_sb.h +6 -0
index 0bc6a6c..55a0c1d 100644
@@ -29,6 +29,11 @@
 
 struct jffs2_inodirty;
 
+struct jffs2_mount_opts {
+	bool override_compr;
+	unsigned int compr;
+};
+
 /* A struct for the overall file system control.  Pointers to
    jffs2_sb_info structs are named `c' in the source code.
    Nee jffs_control

@@ -126,6 +131,7 @@ struct jffs2_sb_info {
 #endif
 
 	struct jffs2_summary *summary;		/* Summary information */
+	struct jffs2_mount_opts mount_opts;
 
 #ifdef CONFIG_JFFS2_FS_XATTR
 #define XATTRINDEX_HASHSIZE	(57)
fs/jffs2/os-linux.h +1 -1
index 6c1755c..ab65ee3 100644
@@ -176,7 +176,7 @@ void jffs2_dirty_inode(struct inode *inode, int flags);
 struct inode *jffs2_new_inode (struct inode *dir_i, umode_t mode,
 			       struct jffs2_raw_inode *ri);
 int jffs2_statfs (struct dentry *, struct kstatfs *);
-int jffs2_remount_fs (struct super_block *, int *, char *);
+int jffs2_do_remount_fs(struct super_block *, int *, char *);
 int jffs2_do_fill_super(struct super_block *sb, void *data, int silent);
 void jffs2_gc_release_inode(struct jffs2_sb_info *c,
 			    struct jffs2_inode_info *f);
fs/jffs2/super.c +97 -0

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Signature · 1 line
1.7.2.5
#1 lore raw
Quoted 11 lines · Andres Salomon

Currently jffs2 has compile-time constants (and .config options) controlling whether or not the various compression/decompression drivers are built in and enabled. This is fine for embedded systems, but it clashes with distribution kernels. Distro kernels tend to turn on everything; this causes OpenFirmware to fall over, as it understands ZLIB-compressed inodes. Booting a kernel that has LZO compression enabled, writing to the boot partition, and then rebooting causes OFW to fail to read the kernel from the filesystem. This is because LZO compression has priority when writing new data to jffs2, if LZO is enabled.

Quoted 5 lines

This patch adds mount option parsing, and a single supported option ("compr=none"). This adds the flexibility of being able to specify which compressor overrides on a per-superblock basis. For now, we can simply disable compression; additional flexibility coming soon.

Pushed both to l2-mtd-2.6.git, thanks!

Signature · 2 lines
Best Regards,
Artem Bityutskiy