commit 6c34f97cb889456c2340a3935d1253f99ec13522
parent a505fd66511db520df12f3fcb83d49b395e4da8a
Author: rsc <rsc>
Date: Mon, 27 Aug 2007 14:23:48 +0000
tell what an inode is
Diffstat:
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs.c b/fs.c
@@ -98,7 +98,12 @@ bfree(int dev, uint b)
brelse(bp);
}
-// Inodes
+// Inodes.
+//
+// An inode is a single, unnamed file in the file system.
+// The inode disk structure holds metadata (the type, device numbers,
+// and data size) along with a list of blocks where the associated
+// data can be found.
//
// The inodes are laid out sequentially on disk immediately after
// the superblock. The kernel keeps a cache of the in-use
@@ -110,9 +115,9 @@ bfree(int dev, uint b)
// When ip->ref falls to zero, the inode is no longer cached.
// It is an error to use an inode without holding a reference to it.
//
-// Inodes can be locked with I_BUSY (like bufs and B_BUSY).
// Processes are only allowed to read and write inode
-// metadata and contents when holding the inode's lock.
+// metadata and contents when holding the inode's lock,
+// represented by the I_BUSY flag in the in-memory copy.
// Because inode locks are held during disk accesses,
// they are implemented using a flag rather than with
// spin locks. Callers are responsible for locking
@@ -123,7 +128,7 @@ bfree(int dev, uint b)
// To give maximum control over locking to the callers,
// the routines in this file that return inode pointers
// return pointers to *unlocked* inodes. It is the callers'
-// responsibility to lock them before using them. A non-zero
+// responsibility to lock them before using them. A non-zero
// ip->ref keeps these unlocked inodes in the cache.
struct {
