diff options
Diffstat (limited to 'fs/ubifs/file.c')
| -rw-r--r-- | fs/ubifs/file.c | 62 |
1 files changed, 30 insertions, 32 deletions
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c index 6d34dc7..2e6481a 100644 --- a/fs/ubifs/file.c +++ b/fs/ubifs/file.c @@ -21,34 +21,32 @@ */ /* - * This file implements VFS file and inode operations of regular files, device + * This file implements VFS file and inode operations for regular files, device * nodes and symlinks as well as address space operations. * - * UBIFS uses 2 page flags: PG_private and PG_checked. PG_private is set if the - * page is dirty and is used for budgeting purposes - dirty pages should not be - * budgeted. The PG_checked flag is set if full budgeting is required for the - * page e.g., when it corresponds to a file hole or it is just beyond the file - * size. The budgeting is done in 'ubifs_write_begin()', because it is OK to - * fail in this function, and the budget is released in 'ubifs_write_end()'. So - * the PG_private and PG_checked flags carry the information about how the page - * was budgeted, to make it possible to release the budget properly. + * UBIFS uses 2 page flags: @PG_private and @PG_checked. @PG_private is set if + * the page is dirty and is used for optimization purposes - dirty pages are + * not budgeted so the flag shows that 'ubifs_write_end()' should not release + * the budget for this page. The @PG_checked flag is set if full budgeting is + * required for the page e.g., when it corresponds to a file hole or it is + * beyond the file size. The budgeting is done in 'ubifs_write_begin()', because + * it is OK to fail in this function, and the budget is released in + * 'ubifs_write_end()'. So the @PG_private and @PG_checked flags carry + * information about how the page was budgeted, to make it possible to release + * the budget properly. * - * A thing to keep in mind: inode's 'i_mutex' is locked in most VFS operations - * we implement. However, this is not true for '->writepage()', which might be - * called with 'i_mutex' unlocked. For example, when pdflush is performing - * write-back, it calls 'writepage()' with unlocked 'i_mutex', although the - * inode has 'I_LOCK' flag in this case. At "normal" work-paths 'i_mutex' is - * locked in '->writepage', e.g. in "sys_write -> alloc_pages -> direct reclaim - * path'. So, in '->writepage()' we are only guaranteed that the page is - * locked. + * A thing to keep in mind: inode @i_mutex is locked in most VFS operations we + * implement. However, this is not true for 'ubifs_writepage()', which may be + * called with @i_mutex unlocked. For example, when pdflush is doing background + * write-back, it calls 'ubifs_writepage()' with unlocked @i_mutex. At "normal" + * work-paths the @i_mutex is locked in 'ubifs_writepage()', e.g. in the + * "sys_write -> alloc_pages -> direct reclaim path". So, in 'ubifs_writepage()' + * we are only guaranteed that the page is locked. * - * Similarly, 'i_mutex' does not have to be locked in readpage(), e.g., - * readahead path does not have it locked ("sys_read -> generic_file_aio_read - * -> ondemand_readahead -> readpage"). In case of readahead, 'I_LOCK' flag is - * not set as well. However, UBIFS disables readahead. - * - * This, for example means that there might be 2 concurrent '->writepage()' - * calls for the same inode, but different inode dirty pages. + * Similarly, @i_mutex is not always locked in 'ubifs_readpage()', e.g., the + * read-ahead path does not lock it ("sys_read -> generic_file_aio_read -> + * ondemand_readahead -> readpage"). In case of readahead, @I_LOCK flag is not + * set as well. However, UBIFS disables readahead. */ #include "ubifs.h" @@ -449,9 +447,9 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping, /* * We change whole page so no need to load it. But we * have to set the @PG_checked flag to make the further - * code the page is new. This might be not true, but it - * is better to budget more that to read the page from - * the media. + * code know that the page is new. This might be not + * true, but it is better to budget more than to read + * the page from the media. */ SetPageChecked(page); skipped_read = 1; @@ -497,8 +495,8 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping, } /* - * Whee, we aquired budgeting quickly - without involving - * garbage-collection, committing or forceing write-back. We return + * Whee, we acquired budgeting quickly - without involving + * garbage-collection, committing or forcing write-back. We return * with @ui->ui_mutex locked if we are appending pages, and unlocked * otherwise. This is an optimization (slightly hacky though). */ @@ -562,7 +560,7 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping, /* * Return 0 to force VFS to repeat the whole operation, or the - * error code if 'do_readpage()' failes. + * error code if 'do_readpage()' fails. */ copied = do_readpage(page); goto out; @@ -1175,11 +1173,11 @@ static int do_truncation(struct ubifs_info *c, struct inode *inode, ui->ui_size = inode->i_size; /* Truncation changes inode [mc]time */ inode->i_mtime = inode->i_ctime = ubifs_current_time(inode); - /* The other attributes may be changed at the same time as well */ + /* Other attributes may be changed at the same time as well */ do_attr_changes(inode, attr); - err = ubifs_jnl_truncate(c, inode, old_size, new_size); mutex_unlock(&ui->ui_mutex); + out_budg: if (budgeted) ubifs_release_budget(c, &req); |