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Date: Wed, 28 Sep 2011 14:39:40 +0800
From: Jeff Liu <jeff.liu@...cle.com>
To: linux-ext4@...r.kernel.org
CC: Yongqiang Yang <xiaoqiangnk@...il.com>,
Sunil Mushran <sunil.mushran@...cle.com>
Subject: [PATCH 2/2 V2] Add SEEK_HOLE/SEEK_DATA support
Add SEEK_HOLE/SEEK_DATA support.
Signed-off-by: Jie Liu <jeff.liu@...cle.com>
---
fs/ext4/ext4.h | 4 ++
fs/ext4/ext4_extents.h | 8 +++++
fs/ext4/extents.c | 75
++++++++++++++++++++++++++++++++++++++++++++++++
fs/ext4/file.c | 15 +++++----
4 files changed, 95 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e717dfd..9eda477 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2222,6 +2222,10 @@ extern int ext4_move_extents(struct file *o_filp,
struct file *d_filp,
__u64 start_orig, __u64 start_donor,
__u64 len, __u64 *moved_len);
+/* extents.c */
+extern int ext4_find_desired_extent(struct inode *inode, loff_t *offset,
+ int origin);
+
/* page-io.c */
extern int __init ext4_init_pageio(void);
extern void ext4_exit_pageio(void);
diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index 095c36f..ca7a339 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -116,6 +116,14 @@ struct ext4_ext_path {
};
/*
+ * Structure for retrieving extent offset for SEEK_DATA/SEEK_HOLE.
+ */
+struct ext4_extent_seek_info {
+ unsigned int origin; /* SEEK_DATA or SEEK_HOLE */
+ loff_t offset; /* input/output offset */
+};
+
+/*
* structure for external API
*/
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 06e88d4..4c78061 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4122,6 +4122,81 @@ static int ext4_ext_fiemap_cb(struct inode
*inode, ext4_lblk_t next,
return EXT_CONTINUE;
}
+/*
+ * Callback function called for each extent to gather SEEK_DATA/SEEK_HOLE
+ * information.
+ */
+static int ext4_ext_seek_cb(struct inode *inode, ext4_lblk_t next,
+ struct ext4_ext_cache *newex,
+ struct ext4_extent *ex, void *data)
+{
+ __u64 logical;
+ int ret = 0;
+ unsigned char blksize_bits;
+ struct ext4_extent_seek_info *ext_seek_info = data;
+
+ blksize_bits = inode->i_sb->s_blocksize_bits;
+ logical = (__u64)newex->ec_block << blksize_bits;
+
+ if (newex->ec_start == 0) {
+ ret = ext4_get_delayed_extent(inode, next, newex, &logical, 0);
+ if (ret == EXT_CONTINUE) {
+ /*
+ * A hole found, return EXT_BREAK and fill ext_seek_info
+ * ->offset with logical for SEEK_HOLE, or just return.
+ */
+ if (ext_seek_info->origin == SEEK_HOLE) {
+ ext_seek_info->offset = logical;
+ return EXT_BREAK;
+ } else {
+ return ret;
+ }
+ }
+ /* found a delayed extent */
+ }
+
+ if (ext_seek_info->origin == SEEK_DATA) {
+ ext_seek_info->offset = logical;
+ return EXT_BREAK;
+ }
+
+ return EXT_CONTINUE;
+}
+
+int ext4_find_desired_extent(struct inode *inode, loff_t *offset, int
origin)
+{
+ ext4_lblk_t start_blk;
+ ext4_lblk_t end_blk;
+ ext4_lblk_t len_blks;
+ struct ext4_extent_seek_info ext_seek_info;
+ unsigned int blkbits = inode->i_sb->s_blocksize_bits;
+ int error = 0;
+
+ /*
+ * FIXME: do we need to support old block based file?
+ * Generally, we would like to gather extents info over
+ * SEEK_DATA/SEEK_HOLE interface for efficient sparse file
+ * read only.
+ */
+ if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
+ return -ENOTSUPP;
+
+ start_blk = *offset >> blkbits;
+ if (start_blk >= EXT_MAX_BLOCKS)
+ return -ENXIO;
+
+ end_blk = i_size_read(inode) >> blkbits;
+ len_blks = ((ext4_lblk_t)end_blk) - start_blk + 1;
+
+ ext_seek_info.origin = origin;
+ error = ext4_ext_walk_space(inode, start_blk, len_blks,
+ ext4_ext_seek_cb, &ext_seek_info);
+ if (!error)
+ *offset = ext_seek_info.offset;
+
+ return error;
+}
+
/* fiemap flags we can handle specified here */
#define EXT4_FIEMAP_FLAGS (FIEMAP_FLAG_SYNC|FIEMAP_FLAG_XATTR)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index e4095e9..58c8c0a 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -219,6 +219,7 @@ loff_t ext4_llseek(struct file *file, loff_t offset,
int origin)
{
struct inode *inode = file->f_mapping->host;
loff_t maxbytes;
+ int ret;
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
@@ -241,21 +242,21 @@ loff_t ext4_llseek(struct file *file, loff_t
offset, int origin)
* In the generic case the entire file is data, so as long as
* offset isn't at the end of the file then the offset is data.
*/
- if (offset >= inode->i_size) {
- mutex_unlock(&inode->i_mutex);
- return -ENXIO;
- }
- break;
case SEEK_HOLE:
/*
* There is a virtual hole at the end of the file, so as long as
* offset isn't i_size or larger, return i_size.
*/
- if (offset >= inode->i_size) {
+ if (offset >= i_size_read(inode)) {
mutex_unlock(&inode->i_mutex);
return -ENXIO;
}
- offset = inode->i_size;
+
+ ret = ext4_find_desired_extent(inode, &offset, origin);
+ if (ret) {
+ mutex_unlock(&inode->i_mutex);
+ return ret;
+ }
break;
}
--
1.7.4.1
--
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