[syslinux:pathbased] fs: add generic getfssec
syslinux-bot for H. Peter Anvin
hpa at zytor.com
Fri Feb 26 12:15:07 PST 2010
Commit-ID: f3e92c92c0a9e16bec3aa3b1c546a01054056861
Gitweb: http://syslinux.zytor.com/commit/f3e92c92c0a9e16bec3aa3b1c546a01054056861
Author: H. Peter Anvin <hpa at zytor.com>
AuthorDate: Fri, 26 Feb 2010 12:11:18 -0800
Committer: H. Peter Anvin <hpa at zytor.com>
CommitDate: Fri, 26 Feb 2010 12:11:18 -0800
fs: add generic getfssec
Add a generic getfssec method which operate on cached extents. This
should avoid the need to each filesystem to implement its own getfssec
loop.
Signed-off-by: H. Peter Anvin <hpa at zytor.com>
---
core/fs/getfssec.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++++
core/include/fs.h | 27 ++++++++-
2 files changed, 181 insertions(+), 2 deletions(-)
diff --git a/core/fs/getfssec.c b/core/fs/getfssec.c
new file mode 100644
index 0000000..e8ae62f
--- /dev/null
+++ b/core/fs/getfssec.c
@@ -0,0 +1,156 @@
+/* ----------------------------------------------------------------------- *
+ *
+ * Copyright 2010 Intel Corporation; author: H. Peter Anvin
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom
+ * the Software is furnished to do so, subject to the following
+ * conditions:
+ *
+ * The above copyright notice and this permission notice shall
+ * be included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * getfssec.c
+ *
+ * Generic getfssec implementation for disk-based filesystems, which
+ * support the populate_next_extent method.
+ *
+ * The expected semantics of populate_next_extent are as follows:
+ *
+ * inode->next_extent.lstart will contain the initial sector number to
+ * be mapped. The routine is expected to populate inode->next_extent.pstart
+ * and inode->next_extent.len. If inode->prev_extent.pstart != EXTENT_VOID
+ * then the routine is allowed to assume inode->prev_extent contains valid
+ * data.
+ *
+ * If the filesystem can map the entire file as a single extent
+ * (e.g. iso9660), then the filesystem can simply insert the extent
+ * information into inode->prev_extent at searchdir/iget time, and leave
+ * populate_next_extent as NULL.
+ *
+ * Note: the filesystem driver is not required to do extent coalescing,
+ * if that is difficult to do; this routine will perform extent lookahead
+ * and coalescing.
+ */
+
+#include <minmax.h>
+#include "fs.h"
+
+static inline sector_t next_psector(sector_t psector, uint32_t skip)
+{
+ if (EXTENT_SPECIAL(psector))
+ return psector;
+ else
+ return psector + skip;
+}
+
+static inline sector_t next_pstart(const struct extent *e)
+{
+ return next_psector(e->pstart, e->len);
+}
+
+uint32_t generic_getfssec(struct file *file, char *buf,
+ int sectors, bool *have_more)
+{
+ struct inode *inode = file->inode;
+ struct fs_info *fs = file->fs;
+ struct disk *disk = fs->fs_dev->disk;
+ uint32_t bytes_read = 0;
+ uint32_t bytes_left = inode->size - file->offset;
+ uint32_t sectors_left =
+ (bytes_left + SECTOR_SIZE(fs) - 1) >> SECTOR_SHIFT(fs);
+ uint32_t lsector;
+
+ if (sectors > sectors_left)
+ sectors = sectors_left;
+
+ lsector = file->offset >> SECTOR_SHIFT(fs);
+
+ if (lsector < inode->this_extent.lstart ||
+ lsector >= inode->this_extent.lstart + inode->this_extent.len) {
+ /* inode->this_extent unusable, maybe prev_extent is... */
+ inode->this_extent = inode->prev_extent;
+ }
+
+ if (lsector < inode->this_extent.lstart ||
+ lsector >= inode->this_extent.lstart + inode->this_extent.len) {
+ /* Still nothing useful... */
+ inode->this_extent.lstart = lsector;
+ inode->this_extent.len = 0;
+ } else {
+ /* We have some usable information */
+ uint32_t delta = lsector - inode->this_extent.lstart;
+ inode->this_extent.lstart = lsector;
+ inode->this_extent.len -= delta;
+ inode->this_extent.pstart
+ = next_psector(inode->this_extent.pstart, delta);
+ }
+
+ while (sectors) {
+ uint32_t chunk;
+ size_t len;
+
+ if (!inode->this_extent.len && inode->next_extent.len &&
+ inode->this_extent.lstart == inode->next_extent.lstart)
+ inode->this_extent = inode->next_extent;
+
+ while (sectors > inode->this_extent.len) {
+ /* Whatever we had before... */
+ inode->prev_extent = inode->next_extent;
+
+ /* Dummy information to make failure returns easier */
+ inode->next_extent.len = 0;
+
+ fs->fs_ops->populate_next_extent(inode);
+
+ if (inode->next_extent.len &&
+ inode->next_extent.pstart == next_pstart(&inode->this_extent)) {
+ /* Coalesce extents and loop */
+ inode->this_extent.len += inode->next_extent.len;
+ } else {
+ /* Discontiguous extents */
+ break;
+ }
+ }
+
+ chunk = min(sectors, inode->this_extent.len);
+ len = chunk << SECTOR_SHIFT(fs);
+
+ if (inode->this_extent.pstart == EXTENT_ZERO) {
+ memset(buf, 0, len);
+ } else {
+ disk->rdwr_sectors(disk, buf, inode->this_extent.pstart, chunk, 0);
+ inode->this_extent.pstart += chunk;
+ }
+
+ buf += len;
+ sectors -= chunk;
+ bytes_read += len;
+ inode->this_extent.lstart += chunk;
+ inode->this_extent.len -= chunk;
+ }
+
+ bytes_read = min(bytes_read, bytes_left);
+ file->offset += bytes_read;
+
+ if (have_more)
+ *have_more = bytes_read < bytes_left;
+
+ return bytes_read;
+}
diff --git a/core/include/fs.h b/core/include/fs.h
index 25219d9..1870de7 100644
--- a/core/include/fs.h
+++ b/core/include/fs.h
@@ -69,10 +69,28 @@ struct fs_ops {
/* the _dir_ stuff */
struct dirent * (*readdir)(struct file *);
+
+ void (*populate_next_extent)(struct inode *);
};
enum inode_mode {I_FILE, I_DIR, I_SYMLINK};
+/*
+ * Extent structure: contains the mapping of some chunk of a file
+ * that is contiguous on disk.
+ */
+struct extent {
+ sector_t pstart; /* Physical start sector */
+ uint32_t lstart; /* Logical start sector */
+ uint32_t len; /* Number of contiguous sectors */
+};
+
+/* Special sector numbers used for struct extent.pstart */
+#define EXTENT_ZERO ((sector_t)-1) /* All-zero extent */
+#define EXTENT_VOID ((sector_t)-2) /* Invalid information */
+
+#define EXTENT_SPECIAL(x) ((x) >= EXTENT_VOID)
+
/*
* The inode structure, including the detail file information
*/
@@ -81,14 +99,15 @@ struct inode {
int refcnt;
int mode; /* FILE , DIR or SYMLINK */
uint32_t size;
+ uint32_t blocks; /* How many blocks the file take */
uint32_t ino; /* Inode number */
uint32_t atime; /* Access time */
uint32_t mtime; /* Modify time */
uint32_t ctime; /* Create time */
uint32_t dtime; /* Delete time */
- int blocks; /* How many blocks the file take */
uint32_t flags;
uint32_t file_acl;
+ struct extent this_extent, prev_extent, next_extent;
char pvt[0]; /* Private filesystem data */
};
@@ -104,7 +123,7 @@ struct file {
uint32_t offset; /* for next read */
};
- /* For the old searhdir method */
+ /* For the old searchdir method */
struct {
struct open_file_t *open_file;/* The fs-specific open file struct */
};
@@ -208,4 +227,8 @@ int generic_load_config(void);
/* close.c */
void generic_close_file(struct file *file);
+/* getfssec.c */
+uint32_t generic_getfssec(struct file *file, char *buf,
+ int sectors, bool *have_more);
+
#endif /* FS_H */
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