Current way of determining whether a symlink is in fast symlink
format is to call ext2fs_inode_data_blocks2(). If number of data
blocks is zero and EXT4_INLINE_DATA_FL flag is not set, then symlink
data must be in inode->i_block.
This heuristic is becoming increasingly hard to maintain because
inode->i_blocks count can also be incremented for blocks used by
extended attributes. Before ea_inode feature, extra block could come
from xattr block, now more blocks can be added because of xattr
inodes.
To address the issue, add a ext2fs_is_fast_symlink() function that
gives a direct answer based on inode->i_size field. This is
equivalent to kernel's ext4_inode_is_fast_symlink() function.
This patch also fixes a few issues related to fast symlink handling:
- Both rdump_symlink() and follow_link() interpreted symlinks with
0 data blocks to always mean fast symlinks. This is incorrect
because symlinks that are stored as inline data also have
0 data blocks. Thus, they try to read everything from
inode->i_block and miss the symlink suffix in inode extra area.
- e2fsck_pass1_check_symlink() had code to handle inode with
EXT4_INLINE_DATA_FL flag twice. The first if block always returns
from the function so the second one is unreachable code.
Suggested-by: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
---
v2: Added Suggested-by to commit message
debugfs/debugfs.c | 55 +++++++++++++++++++++++-----------------------------
debugfs/dump.c | 4 +---
e2fsck/pass1.c | 42 ++++++++-------------------------------
lib/ext2fs/alloc.c | 9 +++++----
lib/ext2fs/ext2fs.h | 1 +
lib/ext2fs/namei.c | 20 ++++++++++++++++---
lib/ext2fs/swapfs.c | 46 +++++++++++++++++++++----------------------
lib/ext2fs/symlink.c | 11 +++++++++++
misc/fuse2fs.c | 9 ++++-----
9 files changed, 94 insertions(+), 103 deletions(-)
diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index cef4ec2834fa..0a4b536bc25a 100644
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -778,41 +778,31 @@ static void dump_inline_data(FILE *out, const char *prefix, ext2_ino_t inode_num
fprintf(out, "%sSize of inline data: %zu\n", prefix, size);
}
-static void dump_fast_link(FILE *out, ext2_ino_t inode_num,
- struct ext2_inode *inode, const char *prefix)
+static void dump_inline_symlink(FILE *out, ext2_ino_t inode_num,
+ struct ext2_inode *inode, const char *prefix)
{
- errcode_t retval = 0;
- char *buf;
+ errcode_t retval;
+ char *buf = NULL;
size_t size;
- if (inode->i_flags & EXT4_INLINE_DATA_FL) {
- retval = ext2fs_inline_data_size(current_fs, inode_num, &size);
- if (retval)
- goto out;
-
- retval = ext2fs_get_memzero(size + 1, &buf);
- if (retval)
- goto out;
+ retval = ext2fs_inline_data_size(current_fs, inode_num, &size);
+ if (retval)
+ goto out;
- retval = ext2fs_inline_data_get(current_fs, inode_num,
- inode, buf, &size);
- if (retval)
- goto out;
- fprintf(out, "%sFast link dest: \"%.*s\"\n", prefix,
- (int)size, buf);
+ retval = ext2fs_get_memzero(size + 1, &buf);
+ if (retval)
+ goto out;
- retval = ext2fs_free_mem(&buf);
- if (retval)
- goto out;
- } else {
- size_t sz = EXT2_I_SIZE(inode);
+ retval = ext2fs_inline_data_get(current_fs, inode_num,
+ inode, buf, &size);
+ if (retval)
+ goto out;
- if (sz > sizeof(inode->i_block))
- sz = sizeof(inode->i_block);
- fprintf(out, "%sFast link dest: \"%.*s\"\n", prefix, (int) sz,
- (char *)inode->i_block);
- }
+ fprintf(out, "%sFast link dest: \"%.*s\"\n", prefix,
+ (int)size, buf);
out:
+ if (buf)
+ ext2fs_free_mem(&buf);
if (retval)
com_err(__func__, retval, "while dumping link destination");
}
@@ -938,9 +928,12 @@ void internal_dump_inode(FILE *out, const char *prefix,
fprintf(out, "Inode checksum: 0x%08x\n", crc);
}
- if (LINUX_S_ISLNK(inode->i_mode) &&
- ext2fs_inode_data_blocks(current_fs, inode) == 0)
- dump_fast_link(out, inode_num, inode, prefix);
+ if (LINUX_S_ISLNK(inode->i_mode) && ext2fs_is_fast_symlink(inode))
+ fprintf(out, "%sFast link dest: \"%.*s\"\n", prefix,
+ (int)EXT2_I_SIZE(inode), (char *)inode->i_block);
+ else if (LINUX_S_ISLNK(inode->i_mode) &&
+ (inode->i_flags & EXT4_INLINE_DATA_FL))
+ dump_inline_symlink(out, inode_num, inode, prefix);
else if (LINUX_S_ISBLK(inode->i_mode) || LINUX_S_ISCHR(inode->i_mode)) {
int major, minor;
const char *devnote;
diff --git a/debugfs/dump.c b/debugfs/dump.c
index 4d3865153ce0..4d5daf0ac5eb 100644
--- a/debugfs/dump.c
+++ b/debugfs/dump.c
@@ -208,9 +208,7 @@ static void rdump_symlink(ext2_ino_t ino, struct ext2_inode *inode,
goto errout;
}
- /* Apparently, this is the right way to detect and handle fast
- * symlinks; see do_stat() in debugfs.c. */
- if (ext2fs_inode_data_blocks2(current_fs, inode) == 0)
+ if (ext2fs_is_fast_symlink(inode))
strcpy(buf, (char *) inode->i_block);
else {
unsigned bytes = inode->i_size;
diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index 422a3d699111..dd650427795c 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -177,7 +177,6 @@ int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
{
unsigned int len;
int i;
- blk64_t blocks;
ext2_extent_handle_t handle;
struct ext2_extent_info info;
struct ext2fs_extent extent;
@@ -221,12 +220,15 @@ int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
return 1;
}
- blocks = ext2fs_inode_data_blocks2(fs, inode);
- if (blocks) {
- if (inode->i_flags & EXT4_INLINE_DATA_FL)
+ if (ext2fs_is_fast_symlink(inode)) {
+ if (inode->i_size >= sizeof(inode->i_block))
+ return 0;
+
+ len = strnlen((char *)inode->i_block, sizeof(inode->i_block));
+ if (len == sizeof(inode->i_block))
return 0;
+ } else {
if ((inode->i_size >= fs->blocksize) ||
- (blocks != fs->blocksize >> 9) ||
(inode->i_block[0] < fs->super->s_first_data_block) ||
(inode->i_block[0] >= ext2fs_blocks_count(fs->super)))
return 0;
@@ -245,34 +247,6 @@ int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
}
if (len == fs->blocksize)
return 0;
- } else if (inode->i_flags & EXT4_INLINE_DATA_FL) {
- char *inline_buf = NULL;
- size_t inline_sz = 0;
-
- if (ext2fs_inline_data_size(fs, ino, &inline_sz))
- return 0;
- if (inode->i_size != inline_sz)
- return 0;
- if (ext2fs_get_mem(inline_sz + 1, &inline_buf))
- return 0;
- i = 0;
- if (ext2fs_inline_data_get(fs, ino, inode, inline_buf, NULL))
- goto exit_inline;
- inline_buf[inline_sz] = 0;
- len = strnlen(inline_buf, inline_sz);
- if (len != inline_sz)
- goto exit_inline;
- i = 1;
-exit_inline:
- ext2fs_free_mem(&inline_buf);
- return i;
- } else {
- if (inode->i_size >= sizeof(inode->i_block))
- return 0;
-
- len = strnlen((char *)inode->i_block, sizeof(inode->i_block));
- if (len == sizeof(inode->i_block))
- return 0;
}
if (len != inode->i_size)
if ((inode->i_flags & EXT4_ENCRYPT_FL) == 0)
@@ -1787,7 +1761,7 @@ void e2fsck_pass1(e2fsck_t ctx)
if (inode->i_flags & EXT4_INLINE_DATA_FL) {
FINISH_INODE_LOOP(ctx, ino, &pctx, failed_csum);
continue;
- } else if (ext2fs_inode_data_blocks(fs, inode) == 0) {
+ } else if (ext2fs_is_fast_symlink(inode)) {
ctx->fs_fast_symlinks_count++;
check_blocks(ctx, &pctx, block_buf);
FINISH_INODE_LOOP(ctx, ino, &pctx, failed_csum);
diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c
index af214106852f..3fd921679286 100644
--- a/lib/ext2fs/alloc.c
+++ b/lib/ext2fs/alloc.c
@@ -353,10 +353,11 @@ blk64_t ext2fs_find_inode_goal(ext2_filsys fs, ext2_ino_t ino,
ext2_extent_handle_t handle = NULL;
errcode_t err;
- if (inode == NULL || ext2fs_inode_data_blocks2(fs, inode) == 0)
- goto no_blocks;
-
- if (inode->i_flags & EXT4_INLINE_DATA_FL)
+ /* Make sure data stored in inode->i_block is neither fast symlink nor
+ * inline data.
+ */
+ if (inode == NULL || ext2fs_is_fast_symlink(inode) ||
+ inode->i_flags & EXT4_INLINE_DATA_FL)
goto no_blocks;
if (inode->i_flags & EXT4_EXTENTS_FL) {
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index c18ea5f827ad..0106d705e12c 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -1603,6 +1603,7 @@ errcode_t ext2fs_unlink(ext2_filsys fs, ext2_ino_t dir, const char *name,
/* symlink.c */
errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino,
const char *name, const char *target);
+int ext2fs_is_fast_symlink(struct ext2_inode *inode);
/* mmp.c */
errcode_t ext2fs_mmp_read(ext2_filsys fs, blk64_t mmp_blk, void *buf);
diff --git a/lib/ext2fs/namei.c b/lib/ext2fs/namei.c
index 307aecc88d87..d485a7209772 100644
--- a/lib/ext2fs/namei.c
+++ b/lib/ext2fs/namei.c
@@ -50,7 +50,21 @@ static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
if (link_count++ >= EXT2FS_MAX_NESTED_LINKS)
return EXT2_ET_SYMLINK_LOOP;
- if (ext2fs_inode_data_blocks(fs,&ei)) {
+ if (ext2fs_is_fast_symlink(&ei))
+ pathname = (char *)&(ei.i_block[0]);
+ else if (ei.i_flags & EXT4_INLINE_DATA_FL) {
+ retval = ext2fs_get_memzero(ei.i_size, &buffer);
+ if (retval)
+ return retval;
+
+ retval = ext2fs_inline_data_get(fs, inode,
+ &ei, buffer, NULL);
+ if (retval) {
+ ext2fs_free_mem(&buffer);
+ return retval;
+ }
+ pathname = buffer;
+ } else {
retval = ext2fs_bmap2(fs, inode, &ei, NULL, 0, 0, NULL, &blk);
if (retval)
return retval;
@@ -65,8 +79,8 @@ static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
return retval;
}
pathname = buffer;
- } else
- pathname = (char *)&(ei.i_block[0]);
+ }
+
retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
link_count, buf, res_inode);
if (buffer)
diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
index 2d05ee7b995b..4522045dd1ca 100644
--- a/lib/ext2fs/swapfs.c
+++ b/lib/ext2fs/swapfs.c
@@ -210,18 +210,24 @@ void ext2fs_swap_inode_full(ext2_filsys fs, struct ext2_inode_large *t,
struct ext2_inode_large *f, int hostorder,
int bufsize)
{
- unsigned i, has_data_blocks, extra_isize, attr_magic;
- int has_extents = 0;
- int has_inline_data = 0;
- int islnk = 0;
+ unsigned i, extra_isize, attr_magic;
+ int has_extents, has_inline_data, islnk, fast_symlink;
int inode_size;
__u32 *eaf, *eat;
- if (hostorder && LINUX_S_ISLNK(f->i_mode))
- islnk = 1;
+ /*
+ * Note that t and f may point to the same address. That's why
+ * if (hostorder) condition is executed before swab calls and
+ * if (!hostorder) afterwards.
+ */
+ if (hostorder) {
+ islnk = LINUX_S_ISLNK(f->i_mode);
+ fast_symlink = ext2fs_is_fast_symlink(EXT2_INODE(f));
+ has_extents = (f->i_flags & EXT4_EXTENTS_FL) != 0;
+ has_inline_data = (f->i_flags & EXT4_INLINE_DATA_FL) != 0;
+ }
+
t->i_mode = ext2fs_swab16(f->i_mode);
- if (!hostorder && LINUX_S_ISLNK(t->i_mode))
- islnk = 1;
t->i_uid = ext2fs_swab16(f->i_uid);
t->i_size = ext2fs_swab32(f->i_size);
t->i_atime = ext2fs_swab32(f->i_atime);
@@ -231,27 +237,21 @@ void ext2fs_swap_inode_full(ext2_filsys fs, struct ext2_inode_large *t,
t->i_gid = ext2fs_swab16(f->i_gid);
t->i_links_count = ext2fs_swab16(f->i_links_count);
t->i_file_acl = ext2fs_swab32(f->i_file_acl);
- if (hostorder)
- has_data_blocks = ext2fs_inode_data_blocks(fs,
- (struct ext2_inode *) f);
t->i_blocks = ext2fs_swab32(f->i_blocks);
- if (!hostorder)
- has_data_blocks = ext2fs_inode_data_blocks(fs,
- (struct ext2_inode *) t);
- if (hostorder && (f->i_flags & EXT4_EXTENTS_FL))
- has_extents = 1;
- if (hostorder && (f->i_flags & EXT4_INLINE_DATA_FL))
- has_inline_data = 1;
t->i_flags = ext2fs_swab32(f->i_flags);
- if (!hostorder && (t->i_flags & EXT4_EXTENTS_FL))
- has_extents = 1;
- if (!hostorder && (t->i_flags & EXT4_INLINE_DATA_FL))
- has_inline_data = 1;
t->i_size_high = ext2fs_swab32(f->i_size_high);
+
+ if (!hostorder) {
+ islnk = LINUX_S_ISLNK(t->i_mode);
+ fast_symlink = ext2fs_is_fast_symlink(EXT2_INODE(t));
+ has_extents = (t->i_flags & EXT4_EXTENTS_FL) != 0;
+ has_inline_data = (t->i_flags & EXT4_INLINE_DATA_FL) != 0;
+ }
+
/*
* Extent data and inline data are swapped on access, not here
*/
- if (!has_extents && !has_inline_data && (!islnk || has_data_blocks)) {
+ if (!has_extents && !has_inline_data && (!islnk || !fast_symlink)) {
for (i = 0; i < EXT2_N_BLOCKS; i++)
t->i_block[i] = ext2fs_swab32(f->i_block[i]);
} else if (t != f) {
diff --git a/lib/ext2fs/symlink.c b/lib/ext2fs/symlink.c
index 0e6f9a9fd14e..271aa1ccc134 100644
--- a/lib/ext2fs/symlink.c
+++ b/lib/ext2fs/symlink.c
@@ -174,3 +174,14 @@ cleanup:
ext2fs_free_mem(&block_buf);
return retval;
}
+
+/*
+ * Test whether an inode is a fast symlink.
+ *
+ * A fast symlink has its symlink data stored in inode->i_block.
+ */
+int ext2fs_is_fast_symlink(struct ext2_inode *inode)
+{
+ return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) &&
+ EXT2_I_SIZE(inode) < sizeof(inode->i_block);
+}
\ No newline at end of file
diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index b5897685c466..ee7af419da71 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -863,8 +863,9 @@ static int op_readlink(const char *path, char *buf, size_t len)
len--;
if (inode.i_size < len)
len = inode.i_size;
- if (ext2fs_inode_data_blocks2(fs, &inode) ||
- (inode.i_flags & EXT4_INLINE_DATA_FL)) {
+ if (ext2fs_is_fast_symlink(&inode))
+ memcpy(buf, (char *)inode.i_block, len);
+ else {
/* big/inline symlink */
err = ext2fs_file_open(fs, ino, 0, &file);
@@ -888,9 +889,7 @@ out2:
ret = translate_error(fs, ino, err);
goto out;
}
- } else
- /* inline symlink */
- memcpy(buf, (char *)inode.i_block, len);
+ }
buf[len] = 0;
if (fs_writeable(fs)) {
--
2.13.2.725.g09c95d1e9-goog
