6c46a77d95
- The lmfs_get_block*(3) API calls may now return an error. The idea is to encourage a next generation of file system services to do a better job at dealing with block read errors than the MFS-derived implementations do. These existing file systems have been changed to panic immediately upon getting a block read error, in order to let unchecked errors cause corruption. Note that libbdev already retries failing I/O operations a few times first. - The libminixfs block device I/O module (bio.c) now deals properly with end-of-file conditions on block devices. Since a device or partition size may not be a multiple of the root file system's block size, support for partial block retrival has been added, with a new internal lmfs_get_partial_block(3) call. A new test program, test85, tests the new handling of EOF conditions when reading, writing, and memory-mapping a block device. Change-Id: I05e35b6b8851488328a2679da635ebba0c6d08ce
110 lines
3.7 KiB
C
110 lines
3.7 KiB
C
/* The file system maintains a buffer cache to reduce the number of disk
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* accesses needed. Whenever a read or write to the disk is done, a check is
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* first made to see if the block is in the cache. This file contains some
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* related routines, but the cache is now in libminixfs.
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*/
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#include "fs.h"
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#include <minix/u64.h>
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#include <minix/bdev.h>
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#include <sys/param.h>
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#include <stdlib.h>
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#include <assert.h>
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#include <minix/libminixfs.h>
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#include <math.h>
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#include "buf.h"
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#include "super.h"
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#include "inode.h"
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/*===========================================================================*
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* get_block *
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*===========================================================================*/
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struct buf *get_block(dev_t dev, block_t block, int how)
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{
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/* Wrapper routine for lmfs_get_block(). This MFS implementation does not deal
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* well with block read errors pretty much anywhere. To prevent corruption due
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* to unchecked error conditions, we panic upon an I/O failure here.
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*/
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struct buf *bp;
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int r;
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if ((r = lmfs_get_block(&bp, dev, block, how)) != OK && r != ENOENT)
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panic("MFS: error getting block (%llu,%u): %d", dev, block, r);
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assert(r == OK || how == PEEK);
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return (r == OK) ? bp : NULL;
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}
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/*===========================================================================*
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* alloc_zone *
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*===========================================================================*/
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zone_t alloc_zone(
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dev_t dev, /* device where zone wanted */
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zone_t z /* try to allocate new zone near this one */
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)
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{
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/* Allocate a new zone on the indicated device and return its number. */
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bit_t b, bit;
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struct super_block *sp;
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static int print_oos_msg = 1;
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/* Note that the routine alloc_bit() returns 1 for the lowest possible
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* zone, which corresponds to sp->s_firstdatazone. To convert a value
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* between the bit number, 'b', used by alloc_bit() and the zone number, 'z',
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* stored in the inode, use the formula:
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* z = b + sp->s_firstdatazone - 1
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* Alloc_bit() never returns 0, since this is used for NO_BIT (failure).
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*/
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sp = get_super(dev);
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/* If z is 0, skip initial part of the map known to be fully in use. */
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if (z == sp->s_firstdatazone) {
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bit = sp->s_zsearch;
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} else {
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bit = (bit_t) (z - (sp->s_firstdatazone - 1));
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}
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b = alloc_bit(sp, ZMAP, bit);
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if (b == NO_BIT) {
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err_code = ENOSPC;
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if (print_oos_msg)
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printf("No space on device %d/%d\n", major(sp->s_dev),
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minor(sp->s_dev));
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print_oos_msg = 0; /* Don't repeat message */
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return(NO_ZONE);
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}
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print_oos_msg = 1;
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if (z == sp->s_firstdatazone) sp->s_zsearch = b; /* for next time */
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return( (zone_t) (sp->s_firstdatazone - 1) + (zone_t) b);
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}
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/*===========================================================================*
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* free_zone *
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*===========================================================================*/
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void free_zone(
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dev_t dev, /* device where zone located */
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zone_t numb /* zone to be returned */
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)
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{
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/* Return a zone. */
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register struct super_block *sp;
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bit_t bit;
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/* Locate the appropriate super_block and return bit. */
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sp = get_super(dev);
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if (numb < sp->s_firstdatazone || numb >= sp->s_zones) return;
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bit = (bit_t) (numb - (zone_t) (sp->s_firstdatazone - 1));
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free_bit(sp, ZMAP, bit);
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if (bit < sp->s_zsearch) sp->s_zsearch = bit;
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/* Also tell libminixfs, so that 1) if it has a block for this bit, it can
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* mark it as clean, thus reducing useless writes, and 2) it can tell VM that
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* any previous inode association is to be broken for this block, so that the
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* block will not be mapped in erroneously later on.
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*/
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assert(sp->s_log_zone_size == 0); /* otherwise we need a loop here.. */
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lmfs_free_block(dev, (block_t)numb);
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}
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