diff options
| -rw-r--r-- | fs/ubifs/io.c | 181 |
1 files changed, 137 insertions, 44 deletions
diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c index 7c2a014b59f9..dfd168b7807e 100644 --- a/fs/ubifs/io.c +++ b/fs/ubifs/io.c @@ -31,6 +31,26 @@ * buffer is full or when it is not used for some time (by timer). This is * similar to the mechanism is used by JFFS2. * + * UBIFS distinguishes between minimum write size (@c->min_io_size) and maximum + * write size (@c->max_write_size). The latter is the maximum amount of bytes + * the underlying flash is able to program at a time, and writing in + * @c->max_write_size units should presumably be faster. Obviously, + * @c->min_io_size <= @c->max_write_size. Write-buffers are of + * @c->max_write_size bytes in size for maximum performance. However, when a + * write-buffer is flushed, only the portion of it (aligned to @c->min_io_size + * boundary) which contains data is written, not the whole write-buffer, + * because this is more space-efficient. + * + * This optimization adds few complications to the code. Indeed, on the one + * hand, we want to write in optimal @c->max_write_size bytes chunks, which + * also means aligning writes at the @c->max_write_size bytes offsets. On the + * other hand, we do not want to waste space when synchronizing the write + * buffer, so during synchronization we writes in smaller chunks. And this makes + * the next write offset to be not aligned to @c->max_write_size bytes. So the + * have to make sure that the write-buffer offset (@wbuf->offs) becomes aligned + * to @c->max_write_size bytes again. We do this by temporarily shrinking + * write-buffer size (@wbuf->size). + * * Write-buffers are defined by 'struct ubifs_wbuf' objects and protected by * mutexes defined inside these objects. Since sometimes upper-level code * has to lock the write-buffer (e.g. journal space reservation code), many @@ -46,8 +66,8 @@ * UBIFS uses padding when it pads to the next min. I/O unit. In this case it * uses padding nodes or padding bytes, if the padding node does not fit. * - * All UBIFS nodes are protected by CRC checksums and UBIFS checks all nodes - * every time they are read from the flash media. + * All UBIFS nodes are protected by CRC checksums and UBIFS checks CRC when + * they are read from the flash media. */ #include <linux/crc32.h> @@ -347,11 +367,17 @@ static void cancel_wbuf_timer_nolock(struct ubifs_wbuf *wbuf) * * This function synchronizes write-buffer @buf and returns zero in case of * success or a negative error code in case of failure. + * + * Note, although write-buffers are of @c->max_write_size, this function does + * not necessarily writes all @c->max_write_size bytes to the flash. Instead, + * if the write-buffer is only partially filled with data, only the used part + * of the write-buffer (aligned on @c->min_io_size boundary) is synchronized. + * This way we waste less space. */ int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf) { struct ubifs_info *c = wbuf->c; - int err, dirt; + int err, dirt, sync_len; cancel_wbuf_timer_nolock(wbuf); if (!wbuf->used || wbuf->lnum == -1) @@ -366,26 +392,48 @@ int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf) ubifs_assert(wbuf->size <= c->max_write_size); ubifs_assert(wbuf->size % c->min_io_size == 0); ubifs_assert(!c->ro_media && !c->ro_mount); + if (c->leb_size - wbuf->offs >= c->max_write_size) + ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size )); if (c->ro_error) return -EROFS; - ubifs_pad(c, wbuf->buf + wbuf->used, wbuf->avail); + /* + * Do not write whole write buffer but write only the minimum necessary + * amount of min. I/O units. + */ + sync_len = ALIGN(wbuf->used, c->min_io_size); + dirt = sync_len - wbuf->used; + if (dirt) + ubifs_pad(c, wbuf->buf + wbuf->used, dirt); err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs, - wbuf->size, wbuf->dtype); + sync_len, wbuf->dtype); if (err) { ubifs_err("cannot write %d bytes to LEB %d:%d", - wbuf->size, wbuf->lnum, wbuf->offs); + sync_len, wbuf->lnum, wbuf->offs); dbg_dump_stack(); return err; } - dirt = wbuf->avail; - spin_lock(&wbuf->lock); - wbuf->offs += wbuf->size; - wbuf->avail = c->min_io_size; - wbuf->size = c->min_io_size; + wbuf->offs += sync_len; + /* + * Now @wbuf->offs is not necessarily aligned to @c->max_write_size. + * But our goal is to optimize writes and make sure we write in + * @c->max_write_size chunks and to @c->max_write_size-aligned offset. + * Thus, if @wbuf->offs is not aligned to @c->max_write_size now, make + * sure that @wbuf->offs + @wbuf->size is aligned to + * @c->max_write_size. This way we make sure that after next + * write-buffer flush we are again at the optimal offset (aligned to + * @c->max_write_size). + */ + if (c->leb_size - wbuf->offs < c->max_write_size) + wbuf->size = c->leb_size - wbuf->offs; + else if (wbuf->offs & (c->max_write_size - 1)) + wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs; + else + wbuf->size = c->max_write_size; + wbuf->avail = wbuf->size; wbuf->used = 0; wbuf->next_ino = 0; spin_unlock(&wbuf->lock); @@ -428,8 +476,13 @@ int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs, spin_lock(&wbuf->lock); wbuf->lnum = lnum; wbuf->offs = offs; - wbuf->avail = c->min_io_size; - wbuf->size = c->min_io_size; + if (c->leb_size - wbuf->offs < c->max_write_size) + wbuf->size = c->leb_size - wbuf->offs; + else if (wbuf->offs & (c->max_write_size - 1)) + wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs; + else + wbuf->size = c->max_write_size; + wbuf->avail = wbuf->size; wbuf->used = 0; spin_unlock(&wbuf->lock); wbuf->dtype = dtype; @@ -509,8 +562,9 @@ out_timers: * * This function writes data to flash via write-buffer @wbuf. This means that * the last piece of the node won't reach the flash media immediately if it - * does not take whole minimal I/O unit. Instead, the node will sit in RAM - * until the write-buffer is synchronized (e.g., by timer). + * does not take whole max. write unit (@c->max_write_size). Instead, the node + * will sit in RAM until the write-buffer is synchronized (e.g., by timer, or + * because more data are appended to the write-buffer). * * This function returns zero in case of success and a negative error code in * case of failure. If the node cannot be written because there is no more @@ -533,6 +587,8 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len) ubifs_assert(wbuf->size % c->min_io_size == 0); ubifs_assert(mutex_is_locked(&wbuf->io_mutex)); ubifs_assert(!c->ro_media && !c->ro_mount); + if (c->leb_size - wbuf->offs >= c->max_write_size) + ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size )); if (c->leb_size - wbuf->offs - wbuf->used < aligned_len) { err = -ENOSPC; @@ -561,9 +617,12 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len) goto out; spin_lock(&wbuf->lock); - wbuf->offs += c->min_io_size; - wbuf->avail = c->min_io_size; - wbuf->size = c->min_io_size; + wbuf->offs += wbuf->size; + if (c->leb_size - wbuf->offs >= c->max_write_size) + wbuf->size = c->max_write_size; + else + wbuf->size = c->leb_size - wbuf->offs; + wbuf->avail = wbuf->size; wbuf->used = 0; wbuf->next_ino = 0; spin_unlock(&wbuf->lock); @@ -577,33 +636,57 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len) goto exit; } - /* - * The node is large enough and does not fit entirely within current - * minimal I/O unit. We have to fill and flush write-buffer and switch - * to the next min. I/O unit. - */ - dbg_io("flush jhead %s wbuf to LEB %d:%d", - dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs); - memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail); - err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs, - wbuf->size, wbuf->dtype); - if (err) - goto out; + offs = wbuf->offs; + written = 0; - offs = wbuf->offs + wbuf->size; - len -= wbuf->avail; - aligned_len -= wbuf->avail; - written = wbuf->avail; + if (wbuf->used) { + /* + * The node is large enough and does not fit entirely within + * current available space. We have to fill and flush + * write-buffer and switch to the next max. write unit. + */ + dbg_io("flush jhead %s wbuf to LEB %d:%d", + dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs); + memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail); + err = ubi_leb_write(c->ubi, wbuf->lnum, wbuf->buf, wbuf->offs, + wbuf->size, wbuf->dtype); + if (err) + goto out; + + offs += wbuf->size; + len -= wbuf->avail; + aligned_len -= wbuf->avail; + written += wbuf->avail; + } else if (wbuf->offs & (c->max_write_size - 1)) { + /* + * The write-buffer offset is not aligned to + * @c->max_write_size and @wbuf->size is less than + * @c->max_write_size. Write @wbuf->size bytes to make sure the + * following writes are done in optimal @c->max_write_size + * chunks. + */ + dbg_io("write %d bytes to LEB %d:%d", + wbuf->size, wbuf->lnum, wbuf->offs); + err = ubi_leb_write(c->ubi, wbuf->lnum, buf, wbuf->offs, + wbuf->size, wbuf->dtype); + if (err) + goto out; + + offs += wbuf->size; + len -= wbuf->size; + aligned_len -= wbuf->size; + written += wbuf->size; + } /* - * The remaining data may take more whole min. I/O units, so write the - * remains multiple to min. I/O unit size directly to the flash media. + * The remaining data may take more whole max. write units, so write the + * remains multiple to max. write unit size directly to the flash media. * We align node length to 8-byte boundary because we anyway flash wbuf * if the remaining space is less than 8 bytes. */ - n = aligned_len >> c->min_io_shift; + n = aligned_len >> c->max_write_shift; if (n) { - n <<= c->min_io_shift; + n <<= c->max_write_shift; dbg_io("write %d bytes to LEB %d:%d", n, wbuf->lnum, offs); err = ubi_leb_write(c->ubi, wbuf->lnum, buf + written, offs, n, wbuf->dtype); @@ -619,15 +702,18 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len) if (aligned_len) /* * And now we have what's left and what does not take whole - * min. I/O unit, so write it to the write-buffer and we are + * max. write unit, so write it to the write-buffer and we are * done. */ memcpy(wbuf->buf, buf + written, len); wbuf->offs = offs; + if (c->leb_size - wbuf->offs >= c->max_write_size) + wbuf->size = c->max_write_size; + else + wbuf->size = c->leb_size - wbuf->offs; + wbuf->avail = wbuf->size - aligned_len; wbuf->used = aligned_len; - wbuf->avail = c->min_io_size - aligned_len; - wbuf->size = c->min_io_size; wbuf->next_ino = 0; spin_unlock(&wbuf->lock); @@ -851,11 +937,11 @@ int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf) { size_t size; - wbuf->buf = kmalloc(c->min_io_size, GFP_KERNEL); + wbuf->buf = kmalloc(c->max_write_size, GFP_KERNEL); if (!wbuf->buf) return -ENOMEM; - size = (c->min_io_size / UBIFS_CH_SZ + 1) * sizeof(ino_t); + size = (c->max_write_size / UBIFS_CH_SZ + 1) * sizeof(ino_t); wbuf->inodes = kmalloc(size, GFP_KERNEL); if (!wbuf->inodes) { kfree(wbuf->buf); @@ -865,7 +951,14 @@ int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf) wbuf->used = 0; wbuf->lnum = wbuf->offs = -1; - wbuf->avail = wbuf->size = c->min_io_size; + /* + * If the LEB starts at the max. write size aligned address, then + * write-buffer size has to be set to @c->max_write_size. Otherwise, + * set it to something smaller so that it ends at the closest max. + * write size boundary. + */ + size = c->max_write_size - (c->leb_start % c->max_write_size); + wbuf->avail = wbuf->size = size; wbuf->dtype = UBI_UNKNOWN; wbuf->sync_callback = NULL; mutex_init(&wbuf->io_mutex); |