diff options
Diffstat (limited to 'storeio/dev.c')
| -rw-r--r-- | storeio/dev.c | 459 |
1 files changed, 459 insertions, 0 deletions
diff --git a/storeio/dev.c b/storeio/dev.c new file mode 100644 index 00000000..0a713253 --- /dev/null +++ b/storeio/dev.c @@ -0,0 +1,459 @@ +/* store `device' I/O + + Copyright (C) 1995, 1996, 1998, 1999 Free Software Foundation, Inc. + + Written by Miles Bader <miles@gnu.ai.mit.edu> + + This program is free software; you can redistribute it and/or + modify it under the terms of the GNU General Public License as + published by the Free Software Foundation; either version 2, or (at + your option) any later version. + + This program is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ + +#include <hurd.h> +#include <assert.h> +#include <string.h> +#include <hurd/pager.h> +#include <hurd/store.h> +#include <sys/mman.h> + +#include "dev.h" + +/* These functions deal with the buffer used for doing non-block-aligned I/O. */ + +static inline int +dev_buf_is_active (struct dev *dev) +{ + return dev->buf_offs >= 0; +} + +/* Invalidate DEV's buffer, writing it to disk if necessary. */ +static error_t +dev_buf_discard (struct dev *dev) +{ + if (dev_buf_is_active (dev)) + { + if (dev->buf_dirty) + { + size_t amount; + struct store *store = dev->store; + error_t err = + store_write (store, dev->buf_offs >> store->log2_block_size, + dev->buf, store->block_size, &amount); + if (amount < store->block_size) + err = EIO; + if (err) + return err; + dev->buf_dirty = 0; + } + dev->buf_offs = -1; + } + return 0; +} + +/* Make DEV's buffer active, reading the block from DEV's store which + contains OFFS. */ +static error_t +dev_buf_fill (struct dev *dev, off_t offs) +{ + error_t err; + unsigned block_mask = dev->block_mask; + void *buf = dev->buf; + struct store *store = dev->store; + size_t buf_len = store->block_size; + + if (dev_buf_is_active (dev)) + { + if ((dev->buf_offs & ~block_mask) == (offs & ~block_mask)) + return 0; /* Correct block alredy in buffer. */ + else + { + err = dev_buf_discard (dev); + if (err) + return err; + } + } + + err = store_read (store, offs >> store->log2_block_size, store->block_size, + &buf, &buf_len); + if (err) + return err; + + if (buf != dev->buf) + { + munmap (dev->buf, store->block_size); + dev->buf = buf; + } + + dev->buf_offs = offs & ~block_mask; + + return 0; +} + +/* Do an in-buffer partial-block I/O operation. */ +static error_t +dev_buf_rw (struct dev *dev, size_t buf_offs, size_t *io_offs, size_t *len, + inline error_t (*const buf_rw) (size_t buf_offs, + size_t io_offs, size_t len)) +{ + size_t block_size = dev->store->block_size; + + assert (dev_buf_is_active (dev)); + + if (buf_offs + *len >= block_size) + /* Only part of BUF lies within the buffer (or everything up + to the end of the block, in which case we want to flush + the buffer anyway). */ + { + size_t buf_len = block_size - buf_offs; + error_t err = (*buf_rw) (buf_offs, *io_offs, buf_len); + if (err) + return err; + *io_offs += buf_len; + *len -= buf_len; + return dev_buf_discard (dev); + } + else + /* All I/O is within the block. */ + { + error_t err = (*buf_rw) (buf_offs, *io_offs, *len); + if (err) + return err; + *io_offs += *len; + *len = 0; + return 0; + } +} + +/* Returns a pointer to a new device structure in DEV for the kernel device + NAME, with the given FLAGS. If BLOCK_SIZE is non-zero, it should be the + desired block size, and must be a multiple of the device block size. + If an error occurs, the error code is returned, otherwise 0. */ +error_t +dev_open (struct store_parsed *name, int flags, int inhibit_cache, + struct dev **dev) +{ + error_t err; + struct dev *new = malloc (sizeof (struct dev)); + + if (! new) + return ENOMEM; + + err = store_parsed_open (name, flags, &new->store); + if (err) + { + free (new); + return err; + } + + new->buf = mmap (0, new->store->block_size, PROT_READ|PROT_WRITE, + MAP_ANON, 0, 0); + if (new->buf == (void *) -1) + { + store_free (new->store); + free (new); + return ENOMEM; + } + + new->inhibit_cache = inhibit_cache; + new->owner = 0; + if (!inhibit_cache) + { + new->buf_offs = -1; + rwlock_init (&new->io_lock); + new->block_mask = (1 << new->store->log2_block_size) - 1; + new->pager = 0; + mutex_init (&new->pager_lock); + } + *dev = new; + + return 0; +} + +/* Free DEV and any resources it consumes. */ +void +dev_close (struct dev *dev) +{ + if (!dev->inhibit_cache) + { + if (dev->pager != NULL) + pager_shutdown (dev->pager); + + dev_buf_discard (dev); + + munmap (dev->buf, dev->store->block_size); + } + + store_free (dev->store); + + free (dev); +} + +/* Try and write out any pending writes to DEV. If WAIT is true, will wait + for any paging activity to cease. */ +error_t +dev_sync(struct dev *dev, int wait) +{ + error_t err; + + if (dev->inhibit_cache) + return 0; + + /* Sync any paged backing store. */ + if (dev->pager != NULL) + pager_sync (dev->pager, wait); + + rwlock_writer_lock (&dev->io_lock); + err = dev_buf_discard (dev); + rwlock_writer_unlock (&dev->io_lock); + + return err; +} + +/* Takes care of buffering I/O to/from DEV for a transfer at position OFFS, + length LEN; the amount of I/O sucessfully done is returned in AMOUNT. + BUF_RW is called to do I/O that's entirely inside DEV's internal buffer, + and RAW_RW to do I/O directly to DEV's store. */ +static inline error_t +buffered_rw (struct dev *dev, off_t offs, size_t len, size_t *amount, + inline error_t (* const buf_rw) (size_t buf_offs, + size_t io_offs, size_t len), + inline error_t (* const raw_rw) (off_t offs, + size_t io_offs, size_t len, + size_t *amount)) +{ + error_t err = 0; + unsigned block_mask = dev->block_mask; + unsigned block_size = dev->store->block_size; + size_t io_offs = 0; /* Offset within this I/O operation. */ + unsigned block_offs = offs & block_mask; /* Offset within a block. */ + + rwlock_writer_lock (&dev->io_lock); + + if (block_offs != 0) + /* The start of the I/O isn't block aligned. */ + { + err = dev_buf_fill (dev, offs); + if (! err) + err = dev_buf_rw (dev, block_offs, &io_offs, &len, buf_rw); + } + + if (!err && len > 0) + /* Now the I/O should be block aligned. */ + { + if (len >= block_size) + { + size_t amount; + err = dev_buf_discard (dev); + if (! err) + err = + (*raw_rw) (offs + io_offs, io_offs, len & ~block_mask, &amount); + if (! err) + { + io_offs += amount; + len -= amount; + } + } + if (len > 0 && len < block_size) + /* All full blocks were written successfully, so write + the tail end into the buffer. */ + { + err = dev_buf_fill (dev, offs + io_offs); + if (! err) + err = dev_buf_rw (dev, 0, &io_offs, &len, buf_rw); + } + } + + if (! err) + *amount = io_offs; + + rwlock_writer_unlock (&dev->io_lock); + + return err; +} + +/* Takes care of buffering I/O to/from DEV for a transfer at position OFFS, + length LEN, and direction DIR. BUF_RW is called to do I/O to/from data + buffered in DEV, and RAW_RW to do I/O directly to DEV's store. */ +static inline error_t +dev_rw (struct dev *dev, off_t offs, size_t len, size_t *amount, + inline error_t (* const buf_rw) (size_t buf_offs, + size_t io_offs, size_t len), + inline error_t (* const raw_rw) (off_t offs, + size_t io_offs, size_t len, + size_t *amount)) +{ + error_t err; + unsigned block_mask = dev->block_mask; + + if (offs < 0 || offs > dev->store->size) + return EINVAL; + else if (offs + len > dev->store->size) + len = dev->store->size - offs; + + rwlock_reader_lock (&dev->io_lock); + if (dev_buf_is_active (dev) + || (offs & block_mask) != 0 || (len & block_mask) != 0) + /* Some non-aligned I/O has been done, or is needed, so we need to deal + with DEV's buffer, which means getting an exclusive lock. */ + { + /* Aquire a writer lock instead of a reader lock. Note that other + writers may have aquired the lock by the time we get it. */ + rwlock_reader_unlock (&dev->io_lock); + err = buffered_rw (dev, offs, len, amount, buf_rw, raw_rw); + } + else + /* Only block-aligned I/O is being done, so things are easy. */ + { + err = (*raw_rw) (offs, 0, len, amount); + rwlock_reader_unlock (&dev->io_lock); + } + + return err; +} + +/* Write LEN bytes from BUF to DEV, returning the amount actually written in + AMOUNT. If successful, 0 is returned, otherwise an error code is + returned. */ +error_t +dev_write (struct dev *dev, off_t offs, void *buf, size_t len, + size_t *amount) +{ + error_t buf_write (size_t buf_offs, size_t io_offs, size_t len) + { + bcopy (buf + io_offs, dev->buf + buf_offs, len); + dev->buf_dirty = 1; + return 0; + } + error_t raw_write (off_t offs, size_t io_offs, size_t len, size_t *amount) + { + struct store *store = dev->store; + return + store_write (store, offs >> store->log2_block_size, + buf + io_offs, len, amount); + } + + if (dev->inhibit_cache) + { + /* Under --no-cache, we permit only whole-block writes. + Note that in this case we handle non-power-of-two block sizes. */ + + struct store *store = dev->store; + + if (store->block_size == 0) + /* We don't know the block size, so let the device enforce it. */ + return store_write (dev->store, offs, buf, len, amount); + + if ((offs & (store->block_size - 1)) != 0 + || (len & (store->block_size - 1)) != 0) + /* Not whole blocks. No can do. */ + return EINVAL; /* EIO? */ + + /* Do a direct write to the store. */ + return store_write (dev->store, offs << store->log2_block_size, + buf, len, amount); + } + + return dev_rw (dev, offs, len, amount, buf_write, raw_write); +} + +/* Read up to WHOLE_AMOUNT bytes from DEV, returned in BUF and LEN in the + with the usual mach memory result semantics. If successful, 0 is + returned, otherwise an error code is returned. */ +error_t +dev_read (struct dev *dev, off_t offs, size_t whole_amount, + void **buf, size_t *len) +{ + error_t err; + int allocated_buf = 0; + error_t ensure_buf () + { + if (*len < whole_amount) + { + void *new = mmap (0, whole_amount, PROT_READ|PROT_WRITE, + MAP_ANON, 0, 0); + if (new == (void *) -1) + return errno; + *buf = new; + allocated_buf = 1; + } + return 0; + } + error_t buf_read (size_t buf_offs, size_t io_offs, size_t len) + { + error_t err = ensure_buf (); + if (! err) + bcopy (dev->buf + buf_offs, *buf + io_offs, len); + return err; + } + error_t raw_read (off_t offs, size_t io_offs, size_t len, size_t *amount) + { + struct store *store = dev->store; + off_t addr = offs >> store->log2_block_size; + if (len == whole_amount) + /* Just return whatever the device does. */ + return store_read (store, addr, len, buf, amount); + else + /* This read is returning less than the whole request, so we allocate + a buffer big enough to hold everything, in case we have to + coalesce multiple reads into a single return buffer. */ + { + error_t err = ensure_buf (); + if (! err) + { + void *_req_buf = *buf + io_offs, *req_buf = _req_buf; + size_t req_len = len; + err = store_read (store, addr, len, &req_buf, &req_len); + if (! err) + { + if (req_buf != _req_buf) + /* Copy from wherever the read put it. */ + { + bcopy (req_buf, _req_buf, req_len); + munmap (req_buf, req_len); + } + *amount = req_len; + } + } + return err; + } + } + + if (dev->inhibit_cache) + { + /* Under --no-cache, we permit only whole-block reads. + Note that in this case we handle non-power-of-two block sizes. + We could, that is, but libstore won't have it (see libstore/make.c). + If the device does not report a block size, we let any attempt + through on the assumption the device will enforce its own limits. */ + + struct store *store = dev->store; + + if (store->block_size == 0) + /* We don't know the block size, so let the device enforce it. */ + return store_read (dev->store, offs, whole_amount, buf, len); + + if ((offs & (store->block_size - 1)) != 0 + || (whole_amount & (store->block_size - 1)) != 0) + /* Not whole blocks. No can do. */ + return EINVAL; + + /* Do a direct read from the store. */ + return store_read (dev->store, offs << store->log2_block_size, + whole_amount, buf, len); + } + + err = dev_rw (dev, offs, whole_amount, len, buf_read, raw_read); + if (err && allocated_buf) + munmap (*buf, whole_amount); + + return err; +} |