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author | Wengang Wang <wen.gang.wang@oracle.com> | 2011-07-24 10:36:54 -0700 |
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committer | Sunil Mushran <sunil.mushran@oracle.com> | 2011-07-24 10:36:54 -0700 |
commit | 5cffff9e29866a3de98c2c25135b3199491f93b0 (patch) | |
tree | 11b53cb3ad7cb44adb80f7802a62c145bf713514 /fs/ocfs2/aops.c | |
parent | a035bff6b82aca89c1223e2c614adc2d17ec8aa2 (diff) | |
download | linux-stable-5cffff9e29866a3de98c2c25135b3199491f93b0.tar.gz linux-stable-5cffff9e29866a3de98c2c25135b3199491f93b0.tar.bz2 linux-stable-5cffff9e29866a3de98c2c25135b3199491f93b0.zip |
ocfs2: Fix ocfs2_page_mkwrite()
This patch address two shortcomings in ocfs2_page_mkwrite():
1. Makes the function return better VM_FAULT_* errors.
2. It handles a error that is triggered when a page is dropped from the mapping
due to memory pressure. This patch locks the page to prevent that.
[Patch was cleaned up by Sunil Mushran.]
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Diffstat (limited to 'fs/ocfs2/aops.c')
-rw-r--r-- | fs/ocfs2/aops.c | 51 |
1 files changed, 43 insertions, 8 deletions
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c index c1efe939c774..ff98c169b631 100644 --- a/fs/ocfs2/aops.c +++ b/fs/ocfs2/aops.c @@ -863,6 +863,12 @@ struct ocfs2_write_ctxt { struct page *w_target_page; /* + * w_target_locked is used for page_mkwrite path indicating no unlocking + * against w_target_page in ocfs2_write_end_nolock. + */ + unsigned int w_target_locked:1; + + /* * ocfs2_write_end() uses this to know what the real range to * write in the target should be. */ @@ -895,6 +901,24 @@ void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages) static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc) { + int i; + + /* + * w_target_locked is only set to true in the page_mkwrite() case. + * The intent is to allow us to lock the target page from write_begin() + * to write_end(). The caller must hold a ref on w_target_page. + */ + if (wc->w_target_locked) { + BUG_ON(!wc->w_target_page); + for (i = 0; i < wc->w_num_pages; i++) { + if (wc->w_target_page == wc->w_pages[i]) { + wc->w_pages[i] = NULL; + break; + } + } + mark_page_accessed(wc->w_target_page); + page_cache_release(wc->w_target_page); + } ocfs2_unlock_and_free_pages(wc->w_pages, wc->w_num_pages); brelse(wc->w_di_bh); @@ -1132,20 +1156,17 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping, */ lock_page(mmap_page); + /* Exit and let the caller retry */ if (mmap_page->mapping != mapping) { + WARN_ON(mmap_page->mapping); unlock_page(mmap_page); - /* - * Sanity check - the locking in - * ocfs2_pagemkwrite() should ensure - * that this code doesn't trigger. - */ - ret = -EINVAL; - mlog_errno(ret); + ret = -EAGAIN; goto out; } page_cache_get(mmap_page); wc->w_pages[i] = mmap_page; + wc->w_target_locked = true; } else { wc->w_pages[i] = find_or_create_page(mapping, index, GFP_NOFS); @@ -1160,6 +1181,8 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping, wc->w_target_page = wc->w_pages[i]; } out: + if (ret) + wc->w_target_locked = false; return ret; } @@ -1817,11 +1840,23 @@ try_again: */ ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len, cluster_of_pages, mmap_page); - if (ret) { + if (ret && ret != -EAGAIN) { mlog_errno(ret); goto out_quota; } + /* + * ocfs2_grab_pages_for_write() returns -EAGAIN if it could not lock + * the target page. In this case, we exit with no error and no target + * page. This will trigger the caller, page_mkwrite(), to re-try + * the operation. + */ + if (ret == -EAGAIN) { + BUG_ON(wc->w_target_page); + ret = 0; + goto out_quota; + } + ret = ocfs2_write_cluster_by_desc(mapping, data_ac, meta_ac, wc, pos, len); if (ret) { |