diff options
| -rw-r--r-- | fs/ext4/extents.c | 13 | ||||
| -rw-r--r-- | fs/ext4/inode.c | 47 |
2 files changed, 57 insertions, 3 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 8a59f7b..bcf5d04 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -2287,9 +2287,22 @@ out: } /* + * Block allocation/map/preallocation routine for extents based files + * + * * Need to be called with * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block * (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem) + * + * return > 0, number of of blocks already mapped/allocated + * if create == 0 and these are pre-allocated blocks + * buffer head is unmapped + * otherwise blocks are mapped + * + * return = 0, if plain look up failed (blocks have not been allocated) + * buffer head is unmapped + * + * return < 0, error case. */ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, ext4_lblk_t iblock, diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 34f3eb61..945cbf6 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -908,11 +908,38 @@ out: */ #define DIO_CREDITS 25 + +/* + * + * + * ext4_ext4 get_block() wrapper function + * It will do a look up first, and returns if the blocks already mapped. + * Otherwise it takes the write lock of the i_data_sem and allocate blocks + * and store the allocated blocks in the result buffer head and mark it + * mapped. + * + * If file type is extents based, it will call ext4_ext_get_blocks(), + * Otherwise, call with ext4_get_blocks_handle() to handle indirect mapping + * based files + * + * On success, it returns the number of blocks being mapped or allocate. + * if create==0 and the blocks are pre-allocated and uninitialized block, + * the result buffer head is unmapped. If the create ==1, it will make sure + * the buffer head is mapped. + * + * It returns 0 if plain look up failed (blocks have not been allocated), in + * that casem, buffer head is unmapped + * + * It returns the error in case of allocation failure. + */ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block, unsigned long max_blocks, struct buffer_head *bh, int create, int extend_disksize) { int retval; + + clear_buffer_mapped(bh); + /* * Try to see if we can get the block without requesting * for new file system block. @@ -926,12 +953,26 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block, inode, block, max_blocks, bh, 0, 0); } up_read((&EXT4_I(inode)->i_data_sem)); - if (!create || (retval > 0)) + + /* If it is only a block(s) look up */ + if (!create) + return retval; + + /* + * Returns if the blocks have already allocated + * + * Note that if blocks have been preallocated + * ext4_ext_get_block() returns th create = 0 + * with buffer head unmapped. + */ + if (retval > 0 && buffer_mapped(bh)) return retval; /* - * We need to allocate new blocks which will result - * in i_data update + * New blocks allocate and/or writing to uninitialized extent + * will possibly result in updating i_data, so we take + * the write lock of i_data_sem, and call get_blocks() + * with create == 1 flag. */ down_write((&EXT4_I(inode)->i_data_sem)); /* |
