diff options
Diffstat (limited to 'fs.c')
| -rw-r--r-- | fs.c | 253 |
1 files changed, 148 insertions, 105 deletions
@@ -25,8 +25,6 @@ #define min(a, b) ((a) < (b) ? (a) : (b)) -static void ifree(struct inode*); - // Blocks. // Allocate a disk block. @@ -116,30 +114,25 @@ iinit(void) } // Find the inode with number inum on device dev -// and return an in-memory copy. Loads the inode -// from disk into the in-core table if necessary. -// The returned inode is locked and has its ref count incremented. -// Caller must iput the return value when done with it. +// and return the in-memory copy. The returned inode +// has its reference count incremented (and thus must be +// idecref'ed), but is *unlocked*, meaning that none of the fields +// except dev and inum are guaranteed to be initialized. +// This convention gives the caller maximum control over blocking; +// it also guarantees that iget will not sleep, which is useful in +// the early igetroot and when holding other locked inodes. struct inode* iget(uint dev, uint inum) { struct inode *ip, *empty; - struct dinode *dip; - struct buf *bp; acquire(&icache.lock); - loop: // Try for cached inode. empty = 0; for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){ if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){ - if(ip->busy){ - sleep(ip, &icache.lock); - goto loop; - } ip->ref++; - ip->busy = 1; release(&icache.lock); return ip; } @@ -155,52 +148,61 @@ iget(uint dev, uint inum) ip->dev = dev; ip->inum = inum; ip->ref = 1; - ip->busy = 1; + ip->flags = 0; release(&icache.lock); - bp = bread(dev, IBLOCK(inum)); - dip = &((struct dinode*)(bp->data))[inum % IPB]; - ip->type = dip->type; - ip->major = dip->major; - ip->minor = dip->minor; - ip->nlink = dip->nlink; - ip->size = dip->size; - memmove(ip->addrs, dip->addrs, sizeof(ip->addrs)); - brelse(bp); - return ip; } // Iget the inode for the file system root (/). +// This gets called before there is a current process: it cannot sleep! struct inode* igetroot(void) { - return iget(ROOTDEV, 1); + struct inode *ip; + ip = iget(ROOTDEV, 1); + return ip; } // Lock the given inode. void ilock(struct inode *ip) { + struct buf *bp; + struct dinode *dip; + if(ip->ref < 1) panic("ilock"); acquire(&icache.lock); - while(ip->busy) + while(ip->flags & I_BUSY) sleep(ip, &icache.lock); - ip->busy = 1; + ip->flags |= I_BUSY; release(&icache.lock); + + if(!(ip->flags & I_VALID)){ + bp = bread(ip->dev, IBLOCK(ip->inum)); + dip = &((struct dinode*)(bp->data))[ip->inum % IPB]; + ip->type = dip->type; + ip->major = dip->major; + ip->minor = dip->minor; + ip->nlink = dip->nlink; + ip->size = dip->size; + memmove(ip->addrs, dip->addrs, sizeof(ip->addrs)); + brelse(bp); + ip->flags |= I_VALID; + } } // Unlock the given inode. void iunlock(struct inode *ip) { - if(ip->busy != 1 || ip->ref < 1) + if(!(ip->flags & I_BUSY) || ip->ref < 1) panic("iunlock"); acquire(&icache.lock); - ip->busy = 0; + ip->flags &= ~I_BUSY; wakeup(ip); release(&icache.lock); } @@ -209,19 +211,8 @@ iunlock(struct inode *ip) void iput(struct inode *ip) { - if(ip->ref < 1 || ip->busy != 1) - panic("iput"); - - if((ip->ref == 1) && (ip->nlink == 0)) { - itrunc(ip); - ifree(ip); - } - - acquire(&icache.lock); - ip->ref -= 1; - ip->busy = 0; - wakeup(ip); - release(&icache.lock); + iunlock(ip); + idecref(ip); } // Increment reference count for ip. @@ -229,31 +220,42 @@ iput(struct inode *ip) struct inode* iincref(struct inode *ip) { - ilock(ip); + acquire(&icache.lock); ip->ref++; - iunlock(ip); + release(&icache.lock); return ip; } -// Caller holds reference to unlocked ip. -// Drop reference. +// Caller holds reference to unlocked ip. Drop reference. void idecref(struct inode *ip) { - ilock(ip); - iput(ip); + acquire(&icache.lock); + if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0) { + // inode is no longer used: truncate and free inode. + if(ip->flags & I_BUSY) + panic("idecref busy"); + ip->flags |= I_BUSY; + release(&icache.lock); + // XXX convince rsc that no one will come find this inode. + itrunc(ip); + ip->type = 0; + iupdate(ip); + acquire(&icache.lock); + ip->flags &= ~I_BUSY; + } + ip->ref--; + release(&icache.lock); } // Allocate a new inode with the given type on device dev. struct inode* ialloc(uint dev, short type) { - struct inode *ip; + int inum, ninodes; + struct buf *bp; struct dinode *dip; struct superblock *sb; - int ninodes; - int inum; - struct buf *bp; bp = bread(dev, 1); sb = (struct superblock*)bp->data; @@ -268,8 +270,7 @@ ialloc(uint dev, short type) dip->type = type; bwrite(bp, IBLOCK(inum)); // mark it allocated on the disk brelse(bp); - ip = iget(dev, inum); - return ip; + return iget(dev, inum); } brelse(bp); } @@ -295,15 +296,6 @@ iupdate(struct inode *ip) brelse(bp); } -// Free (delete) the given inode. -// Caller must have ip locked. -static void -ifree(struct inode *ip) -{ - ip->type = 0; - iupdate(ip); -} - // Inode contents // // The contents (data) associated with each inode is stored @@ -465,15 +457,15 @@ writei(struct inode *ip, char *src, uint off, uint n) // set *poff to the byte offset of the directory entry // set *pinum to the inode number // return 0. -int -dirlookup(struct inode *dp, char *name, int namelen, uint *poff, uint *pinum) +struct inode* +dirlookup(struct inode *dp, char *name, int namelen, uint *poff) { - uint off; + uint off, inum; struct buf *bp; struct dirent *de; if(dp->type != T_DIR) - return -1; + return 0; for(off = 0; off < dp->size; off += BSIZE){ bp = bread(dp->dev, bmap(dp, off / BSIZE, 0)); @@ -487,24 +479,30 @@ dirlookup(struct inode *dp, char *name, int namelen, uint *poff, uint *pinum) // entry matches path element if(poff) *poff = off + (uchar*)de - bp->data; - if(pinum) - *pinum = de->inum; + inum = de->inum; brelse(bp); - return 0; + return iget(dp->dev, inum); } } brelse(bp); } - return -1; + return 0; } // Write a new directory entry (name, ino) into the directory dp. // Caller must have locked dp. -void -dirwrite(struct inode *dp, char *name, int namelen, uint ino) +int +dirlink(struct inode *dp, char *name, int namelen, uint ino) { int off; struct dirent de; + struct inode *ip; + + // Double-check that name is not present. + if((ip = dirlookup(dp, name, namelen, 0)) != 0){ + idecref(ip); + return -1; + } // Look for an empty dirent. for(off = 0; off < dp->size; off += sizeof(de)){ @@ -519,9 +517,10 @@ dirwrite(struct inode *dp, char *name, int namelen, uint ino) namelen = DIRSIZ; memmove(de.name, name, namelen); memset(de.name+namelen, 0, DIRSIZ-namelen); - if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) panic("dirwrite"); + + return 0; } // Create a new inode named name inside dp @@ -535,13 +534,19 @@ dircreat(struct inode *dp, char *name, int namelen, short type, short major, sho ip = ialloc(dp->dev, type); if(ip == 0) return 0; + ilock(ip); ip->major = major; ip->minor = minor; ip->size = 0; ip->nlink = 1; iupdate(ip); - - dirwrite(dp, name, namelen, ip->inum); + + if(dirlink(dp, name, namelen, ip->inum) < 0){ + ip->nlink = 0; + iupdate(ip); + iput(ip); + return 0; + } return ip; } @@ -590,17 +595,16 @@ skipelem(char *path, char **name, int *len) struct inode* _namei(char *path, int parent, char **pname, int *pnamelen) { - struct inode *dp; + struct inode *dp, *ip; char *name; int namelen; - uint off, dev, inum; + uint off; if(*path == '/') dp = igetroot(); - else { + else dp = iincref(cp->cwd); - ilock(dp); - } + ilock(dp); while((path = skipelem(path, &name, &namelen)) != 0){ // Truncate names in path to DIRSIZ chars. @@ -617,12 +621,12 @@ _namei(char *path, int parent, char **pname, int *pnamelen) return dp; } - if(dirlookup(dp, name, namelen, &off, &inum) < 0) + if((ip = dirlookup(dp, name, namelen, &off)) == 0) goto fail; - dev = dp->dev; iput(dp); - dp = iget(dev, inum); + ilock(ip); + dp = ip; if(dp->type == 0 || dp->nlink < 1) panic("namei"); } @@ -660,10 +664,6 @@ mknod(char *path, short type, short major, short minor) if((dp = nameiparent(path, &name, &namelen)) == 0) return 0; - if(dirlookup(dp, name, namelen, 0, 0) >= 0){ - iput(dp); - return 0; - } ip = dircreat(dp, name, namelen, type, major, minor); iput(dp); return ip; @@ -675,13 +675,13 @@ unlink(char *path) { struct inode *ip, *dp; struct dirent de; - uint off, inum, dev; + uint off; char *name; int namelen; if((dp = nameiparent(path, &name, &namelen)) == 0) return -1; - if(dirlookup(dp, name, namelen, &off, 0) < 0){ + if((ip = dirlookup(dp, name, namelen, &off)) == 0){ iput(dp); return -1; } @@ -691,20 +691,17 @@ unlink(char *path) // Cannot remove "." or ".." - the 2 and 3 count the trailing NUL. if(memcmp(de.name, ".", 2) == 0 || memcmp(de.name, "..", 3) == 0){ + idecref(ip); iput(dp); return -1; } - inum = de.inum; - memset(&de, 0, sizeof(de)); if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) panic("unlink dir write"); - - dev = dp->dev; iput(dp); - ip = iget(dev, inum); + ilock(ip); if(ip->nlink < 1) panic("unlink nlink < 1"); ip->nlink--; @@ -729,30 +726,76 @@ link(char *old, char *new) return -1; } iunlock(ip); - + if((dp = nameiparent(new, &name, &namelen)) == 0){ idecref(ip); return -1; } - if(dirlookup(dp, name, namelen, 0, 0) >= 0){ - iput(dp); - idecref(ip); - return -1; - } - if(dp->dev != ip->dev){ + if(dp->dev != ip->dev || dirlink(dp, name, namelen, ip->inum) < 0){ idecref(ip); iput(dp); return -1; } + iput(dp); - // LOCKING ERROR HERE! TWO LOCKS HELD AT ONCE. + // XXX write ordering wrong here too. ilock(ip); ip->nlink++; iupdate(ip); + iput(ip); + return 0; +} + +int +mkdir(char *path) +{ + struct inode *dp, *ip; + char *name; + int namelen; + + // XXX write ordering is screwy here- do we care? + if((dp = nameiparent(path, &name, &namelen)) == 0) + return -1; + + if((ip = dircreat(dp, name, namelen, T_DIR, 0, 0)) == 0){ + iput(dp); + return -1; + } + dp->nlink++; + iupdate(dp); - dirwrite(dp, name, namelen, ip->inum); + if(dirlink(ip, ".", 1, ip->inum) < 0 || dirlink(ip, "..", 2, dp->inum) < 0) + panic("mkdir"); iput(dp); iput(ip); return 0; } + +struct inode* +create(char *path) +{ + struct inode *dp, *ip; + char *name; + int namelen; + + if((dp = nameiparent(path, &name, &namelen)) == 0) + return 0; + + if((ip = dirlookup(dp, name, namelen, 0)) != 0){ + iput(dp); + ilock(ip); + if(ip->type == T_DIR){ + iput(ip); + return 0; + } + return ip; + } + if((ip = dircreat(dp, name, namelen, T_FILE, 0, 0)) == 0){ + iput(dp); + return 0; + } + iput(dp); + return ip; +} + |