From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
For dumping a sparse file, ext2fs_file_read2 is defined to expand the interface.
It returns the sizeof hole and we can call lseek64(2) to skip it.
CC: George Spelvin <linux@xxxxxxxxxxx>
CC: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
---
debugfs/dump.c | 14 +++++++++++++-
lib/ext2fs/ext2fs.h | 3 +++
lib/ext2fs/fileio.c | 50 +++++++++++++++++++++++++++++++++++++++-----------
3 files changed, 55 insertions(+), 12 deletions(-)
diff --git a/debugfs/dump.c b/debugfs/dump.c
index 5b2289c..d4483dc 100644
--- a/debugfs/dump.c
+++ b/debugfs/dump.c
@@ -107,6 +107,7 @@ static void dump_file(const char *cmdname, ext2_ino_t ino, int fd,
struct ext2_inode inode;
char *buf = 0;
ext2_file_t e2_file;
+ ext2_off64_t seek;
int nbytes;
unsigned int got, blocksize = current_fs->blocksize;
@@ -124,11 +125,22 @@ static void dump_file(const char *cmdname, ext2_ino_t ino, int fd,
return;
}
while (1) {
- retval = ext2fs_file_read(e2_file, buf, blocksize, &got);
+ /* If fd is stdout, we won't consider a sparse file. */
+ if (fd == 1)
+ retval = ext2fs_file_read(e2_file, buf, blocksize,
+ &got);
+ else
+ retval = ext2fs_file_read2(e2_file, buf, blocksize,
+ &got, &seek);
if (retval)
com_err(cmdname, retval, "while reading ext2 file");
if (got == 0)
break;
+ if (fd != 1) {
+ nbytes = lseek64(fd, blocksize * seek, SEEK_CUR);
+ if (nbytes < 0)
+ com_err(cmdname, errno, "while lseek file");
+ }
nbytes = write(fd, buf, got);
if ((unsigned) nbytes != got)
com_err(cmdname, errno, "while writing file");
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 7ec189e..435b68c 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -1171,6 +1171,9 @@ extern errcode_t ext2fs_file_close(ext2_file_t file);
extern errcode_t ext2fs_file_flush(ext2_file_t file);
extern errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
unsigned int wanted, unsigned int *got);
+extern errcode_t ext2fs_file_read2(ext2_file_t file, void *buf,
+ unsigned int wanted, unsigned int *got,
+ ext2_off64_t *seek);
extern errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
unsigned int nbytes, unsigned int *written);
extern errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
diff --git a/lib/ext2fs/fileio.c b/lib/ext2fs/fileio.c
index 1f7002c..508d15c 100644
--- a/lib/ext2fs/fileio.c
+++ b/lib/ext2fs/fileio.c
@@ -179,20 +179,27 @@ static errcode_t sync_buffer_position(ext2_file_t file)
* If dontfill is true, then skip initializing the buffer since we're
* going to be replacing its entire contents anyway. If set, then the
* function basically only sets file->physblock and EXT2_FILE_BUF_VALID
+ *
+ * If seek is true, it indicates that we need to skip unwritten extents.
+ * When we get an unwritten extent, EXT2_FILE_BUF_VALID won't be set to
+ * tell caller that here is an unwritten extent and its content needn't
+ * be copied.
*/
#define DONTFILL 1
-static errcode_t load_buffer(ext2_file_t file, int dontfill)
+#define SEEK 2
+static errcode_t load_buffer(ext2_file_t file, int flags)
{
ext2_filsys fs = file->fs;
errcode_t retval;
+ int ret_flags;
if (!(file->flags & EXT2_FILE_BUF_VALID)) {
retval = ext2fs_bmap2(fs, file->ino, &file->inode,
- BMAP_BUFFER, 0, file->blockno, 0,
- &file->physblock);
+ BMAP_BUFFER, 0, file->blockno,
+ &ret_flags, &file->physblock);
if (retval)
return retval;
- if (!dontfill) {
+ if (flags != DONTFILL) {
if (file->physblock) {
retval = io_channel_read_blk(fs->io,
file->physblock,
@@ -202,7 +209,9 @@ static errcode_t load_buffer(ext2_file_t file, int dontfill)
} else
memset(file->buf, 0, fs->blocksize);
}
- file->flags |= EXT2_FILE_BUF_VALID;
+ if ((flags != SEEK) ||
+ (!(ret_flags & BMAP_RET_UNINIT) && file->physblock))
+ file->flags |= EXT2_FILE_BUF_VALID;
}
return 0;
}
@@ -227,20 +236,33 @@ errcode_t ext2fs_file_close(ext2_file_t file)
errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
unsigned int wanted, unsigned int *got)
{
+ return ext2fs_file_read2(file, buf, wanted, got, 0);
+}
+
+
+errcode_t ext2fs_file_read2(ext2_file_t file, void *buf,
+ unsigned int wanted, unsigned int *got,
+ ext2_off64_t *seek)
+{
ext2_filsys fs;
errcode_t retval = 0;
unsigned int start, c, count = 0;
__u64 left;
char *ptr = (char *) buf;
+ int seek_cnt = 0;
+ int flags = 0;
EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
fs = file->fs;
+ if (seek)
+ flags = SEEK;
+
while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
retval = sync_buffer_position(file);
if (retval)
goto fail;
- retval = load_buffer(file, 0);
+ retval = load_buffer(file, flags);
if (retval)
goto fail;
@@ -248,20 +270,26 @@ errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
c = fs->blocksize - start;
if (c > wanted)
c = wanted;
- left = EXT2_I_SIZE(&file->inode) - file->pos ;
+ left = EXT2_I_SIZE(&file->inode) - file->pos;
if (c > left)
c = left;
- memcpy(ptr, file->buf+start, c);
file->pos += c;
- ptr += c;
- count += c;
- wanted -= c;
+ if (file->flags & EXT2_FILE_BUF_VALID) {
+ memcpy(ptr, file->buf+start, c);
+ ptr += c;
+ count += c;
+ wanted -= c;
+ } else {
+ seek_cnt++;
+ }
}
fail:
if (got)
*got = count;
+ if (seek)
+ *seek = seek_cnt;
return retval;
}
--
1.7.12.rc2.18.g61b472e
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