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Message-Id: <1358173111-10511-1-git-send-email-wenqing.lz@taobao.com> Date: Mon, 14 Jan 2013 22:18:30 +0800 From: Zheng Liu <gnehzuil.liu@...il.com> To: linux-ext4@...r.kernel.org Cc: "Theodore Ts'o" <tytso@....edu>, Zheng Liu <wenqing.lz@...bao.com> Subject: [PATCH 1/2 v2] libext2fs: introduce lseek SEEK_DATA/HOLE From: Zheng Liu <wenqing.lz@...bao.com> ext2fs_file_llseek is extented to introduce SEEK_DATA/HOLE. In *_data() function it will find the next data, and in *_hole() function it will find the next hole. A new error code called EXT2_ET_SEEK_BEYOND_EOF is define to indicate that the offset is beyond the end of file. Here they need to solve a problem that the caller can not dereference ext2_file_t->pos because this structure is hidden by a typedef. Thus, EXT2_SEEK_OFFSET_INVALID is define to indicate whether or not it will find the data/hole from ext2_file_t->pos. CC: "Theodore Ts'o" <tytso@....edu> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com> --- Hi Ted, ext2fs_file_llseek_data/hole() seem to be weird because ext2_file_t structure is hidden by a typedef. The caller can not dereference it. So I define a marco called EXT2_SEEK_OFFSET_INVALID to let the caller indicate that it find the data/hole from ext2_file_t->pos or from offset. What do you think? Thanks, - Zheng lib/ext2fs/ext2_err.et.in | 3 ++ lib/ext2fs/ext2fs.h | 4 +++ lib/ext2fs/fileio.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 86 insertions(+), 1 deletion(-) diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in index c99a167..f763938 100644 --- a/lib/ext2fs/ext2_err.et.in +++ b/lib/ext2fs/ext2_err.et.in @@ -473,4 +473,7 @@ ec EXT2_ET_UNKNOWN_CSUM, ec EXT2_ET_MMP_CSUM_INVALID, "MMP block checksum does not match MMP block" +ec EXT2_ET_SEEK_BEYOND_EOF, + "lseek beyond the EOF" + end diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h index 7139b4d..474049f 100644 --- a/lib/ext2fs/ext2fs.h +++ b/lib/ext2fs/ext2fs.h @@ -160,6 +160,10 @@ typedef struct ext2_file *ext2_file_t; #define EXT2_SEEK_SET 0 #define EXT2_SEEK_CUR 1 #define EXT2_SEEK_END 2 +#define EXT2_SEEK_DATA 3 +#define EXT2_SEEK_HOLE 4 + +#define EXT2_SEEK_OFFSET_INVALID -1 /* * Flags for the ext2_filsys structure and for ext2fs_open() diff --git a/lib/ext2fs/fileio.c b/lib/ext2fs/fileio.c index 1f7002c..ab33290 100644 --- a/lib/ext2fs/fileio.c +++ b/lib/ext2fs/fileio.c @@ -312,10 +312,84 @@ fail: return retval; } +static errcode_t ext2fs_file_llseek_data(ext2_file_t file, __u64 offset) +{ + int ret_flags, flag = 1; + ext2_filsys fs = file->fs; + errcode_t retval; + + /* + * If offset == EXT2_SEEK_OFFSET_INVALID, that means that + * the caller wants to find the data from file->pos. + */ + offset = offset != EXT2_SEEK_OFFSET_INVALID ? offset : file->pos; + file->blockno = offset / fs->blocksize; + while (file->blockno * fs->blocksize < EXT2_I_SIZE(&file->inode)) { + retval = ext2fs_bmap2(fs, file->ino, &file->inode, + BMAP_BUFFER, 0, file->blockno, + &ret_flags, &file->physblock); + if (retval) + return retval; + if (file->physblock == 0 || (ret_flags & BMAP_RET_UNINIT)) { + file->blockno++; + flag = 0; + } else { + if (flag) + file->pos = offset; + else + file->pos = file->blockno * fs->blocksize; + break; + } + } + + /* notify the caller that there is no any data */ + if (file->blockno * fs->blocksize >= EXT2_I_SIZE(&file->inode)) + return EXT2_ET_SEEK_BEYOND_EOF; + + return 0; +} + +static errcode_t ext2fs_file_llseek_hole(ext2_file_t file, __u64 offset) +{ + int ret_flags, flag = 1; + ext2_filsys fs = file->fs; + errcode_t retval; + + /* + * If offset == EXT2_SEEK_OFFSET_INVALID, that means that + * the caller wants to find the hole from file->pos. + */ + offset = offset != EXT2_SEEK_OFFSET_INVALID ? offset : file->pos; + if (offset >= EXT2_I_SIZE(&file->inode)) + return EXT2_ET_SEEK_BEYOND_EOF; + + file->blockno = offset / fs->blocksize; + while (file->blockno * fs->blocksize < EXT2_I_SIZE(&file->inode)) { + retval = ext2fs_bmap2(fs, file->ino, &file->inode, + BMAP_BUFFER, 0, file->blockno, + &ret_flags, &file->physblock); + if (retval) + return retval; + if (file->physblock == 0 || (ret_flags & BMAP_RET_UNINIT)) { + if (flag) + file->pos = offset; + else + file->pos = file->blockno * fs->blocksize; + break; + } else { + file->blockno++; + flag = 0; + } + } + + return 0; +} + errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset, int whence, __u64 *ret_pos) { EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); + errcode_t retval = 0; if (whence == EXT2_SEEK_SET) file->pos = offset; @@ -323,13 +397,17 @@ errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset, file->pos += offset; else if (whence == EXT2_SEEK_END) file->pos = EXT2_I_SIZE(&file->inode) + offset; + else if (whence == EXT2_SEEK_DATA) + retval = ext2fs_file_llseek_data(file, offset); + else if (whence == EXT2_SEEK_HOLE) + retval = ext2fs_file_llseek_hole(file, offset); else return EXT2_ET_INVALID_ARGUMENT; if (ret_pos) *ret_pos = file->pos; - return 0; + return retval; } errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset, -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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