diff options
Diffstat (limited to 'fs/cramfs/inode.c')
| -rw-r--r-- | fs/cramfs/inode.c | 57 |
1 files changed, 31 insertions, 26 deletions
diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c index 279b0bfef..3f51c2aa1 100644 --- a/fs/cramfs/inode.c +++ b/fs/cramfs/inode.c @@ -84,15 +84,17 @@ static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inod #define NEXT_BUFFER(_ix) ((_ix) ^ 1) /* - * BLKS_PER_BUF_SHIFT must be at least 1 to allow for "compressed" - * data that takes up more space than the original. 1 is guaranteed - * to suffice, though. Larger values provide more read-ahead and - * proportionally less wastage at the end of the buffer. + * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" + * data that takes up more space than the original and with unlucky + * alignment. */ -#define BLKS_PER_BUF_SHIFT (2) -#define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) -static unsigned char read_buffers[READ_BUFFERS][BLKS_PER_BUF][PAGE_CACHE_SIZE]; +#define BLKS_PER_BUF_SHIFT (2) +#define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) +#define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE) + +static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; static unsigned buffer_blocknr[READ_BUFFERS]; +static struct super_block * buffer_dev[READ_BUFFERS]; static int next_buffer = 0; /* @@ -102,19 +104,27 @@ static int next_buffer = 0; static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) { struct buffer_head * bh_array[BLKS_PER_BUF]; - unsigned i, blocknr, last_blocknr, buffer; + unsigned i, blocknr, buffer; + char *data; if (!len) return NULL; blocknr = offset >> PAGE_CACHE_SHIFT; - last_blocknr = (offset + len - 1) >> PAGE_CACHE_SHIFT; - if (last_blocknr - blocknr >= BLKS_PER_BUF) - goto eek; resume: offset &= PAGE_CACHE_SIZE - 1; + + /* Check if an existing buffer already has the data.. */ for (i = 0; i < READ_BUFFERS; i++) { - if ((blocknr >= buffer_blocknr[i]) && - (last_blocknr - buffer_blocknr[i] < BLKS_PER_BUF)) - return &read_buffers[i][blocknr - buffer_blocknr[i]][offset]; + unsigned int blk_offset; + + if (buffer_dev[i] != sb) + continue; + if (blocknr < buffer_blocknr[i]) + continue; + blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT; + blk_offset += offset; + if (blk_offset + len > BUFFER_SIZE) + continue; + return read_buffers[i] + blk_offset; } /* Ok, read in BLKS_PER_BUF pages completely first. */ @@ -125,24 +135,19 @@ static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned i buffer = next_buffer; next_buffer = NEXT_BUFFER(buffer); buffer_blocknr[buffer] = blocknr; + buffer_dev[buffer] = sb; + + data = read_buffers[buffer]; for (i = 0; i < BLKS_PER_BUF; i++) { struct buffer_head * bh = bh_array[i]; if (bh) { - memcpy(read_buffers[buffer][i], bh->b_data, PAGE_CACHE_SIZE); + memcpy(data, bh->b_data, PAGE_CACHE_SIZE); bforget(bh); } else - memset(read_buffers[buffer][i], 0, PAGE_CACHE_SIZE); + memset(data, 0, PAGE_CACHE_SIZE); + data += PAGE_CACHE_SIZE; } - return read_buffers[buffer][0] + offset; - - eek: - printk(KERN_ERR - "cramfs (device %s): requested chunk (%u:+%u) bigger than buffer\n", - bdevname(sb->s_dev), offset, len); - /* TODO: return EIO to process or kill the current process - instead of resuming. */ - *((int *)0) = 0; /* XXX: doesn't work on all archs */ - goto resume; + return read_buffers[buffer] + offset; } |