fscache: Pass object size in rather than calling back for it
Pass the object size in to fscache_acquire_cookie() and fscache_write_page() rather than the netfs providing a callback by which it can be received. This makes it easier to update the size of the object when a new page is written that extends the object. The current object size is also passed by fscache to the check_aux function, obviating the need to store it in the aux data. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Anna Schumaker <anna.schumaker@netapp.com> Tested-by: Steve Dickson <steved@redhat.com>
This commit is contained in:
David Howells
@@ -129,12 +129,10 @@ To define an object, a structure of the following type should be filled out:
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const void *parent_netfs_data,
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const void *cookie_netfs_data);
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void (*get_attr)(const void *cookie_netfs_data,
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uint64_t *size);
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enum fscache_checkaux (*check_aux)(void *cookie_netfs_data,
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const void *data,
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uint16_t datalen);
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uint16_t datalen,
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loff_t object_size);
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void (*get_context)(void *cookie_netfs_data, void *context);
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@@ -179,16 +177,7 @@ This has the following fields:
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cache in the parent's list will be chosen, or failing that, the first
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cache in the master list.
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(4) A function to retrieve attribute data from the netfs [optional].
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This function will be called with the netfs data that was passed to the
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cookie acquisition function. It should return the size of the file if
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this is a data file. The size may be used to govern how much cache must
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be reserved for this file in the cache.
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If the function is absent, a file size of 0 is assumed.
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(5) A function to check the auxiliary data [optional].
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(4) A function to check the auxiliary data [optional].
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This function will be called to check that a match found in the cache for
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this object is valid. For instance with AFS it could check the auxiliary
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@@ -198,6 +187,9 @@ This has the following fields:
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If this function is absent, it will be assumed that matching objects in a
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cache are always valid.
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The function is also passed the cache's idea of the object size and may
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use this to manage coherency also.
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If present, the function should return one of the following values:
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(*) FSCACHE_CHECKAUX_OKAY - the entry is okay as is
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@@ -207,7 +199,7 @@ This has the following fields:
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This function can also be used to extract data from the auxiliary data in
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the cache and copy it into the netfs's structures.
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(6) A pair of functions to manage contexts for the completion callback
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(5) A pair of functions to manage contexts for the completion callback
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[optional].
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The cache read/write functions are passed a context which is then passed
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@@ -221,7 +213,7 @@ This has the following fields:
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required for indices as indices may not contain data. These functions may
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be called in interrupt context and so may not sleep.
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(7) A function to mark a page as retaining cache metadata [optional].
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(6) A function to mark a page as retaining cache metadata [optional].
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This is called by the cache to indicate that it is retaining in-memory
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information for this page and that the netfs should uncache the page when
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@@ -233,7 +225,7 @@ This has the following fields:
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This function is not required for indices as they're not permitted data.
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(8) A function to unmark all the pages retaining cache metadata [mandatory].
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(7) A function to unmark all the pages retaining cache metadata [mandatory].
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This is called by FS-Cache to indicate that a backing store is being
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unbound from a cookie and that all the marks on the pages should be
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@@ -310,6 +302,7 @@ the path to the file:
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const void *aux_data,
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size_t aux_data_len,
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void *netfs_data,
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loff_t object_size,
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bool enable);
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This function creates an index entry in the index represented by parent,
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@@ -326,6 +319,10 @@ The netfs may pass an arbitrary value in netfs_data and this will be presented
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to it in the event of any calling back. This may also be used in tracing or
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logging of messages.
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The cache tracks the size of the data attached to an object and this set to be
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object_size. For indices, this should be 0. This value will be passed to the
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->check_aux() callback.
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Note that this function never returns an error - all errors are handled
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internally. It may, however, return NULL to indicate no cookie. It is quite
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acceptable to pass this token back to this function as the parent to another
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@@ -349,7 +346,7 @@ entry would have a dependent inode containing volume mappings within this cell:
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&afs_cell_cache_index_def,
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cell->name, strlen(cell->name),
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NULL, 0,
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cell, true);
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cell, 0, true);
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And then a particular volume could be added to that index by ID, creating
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another index for vnodes (AFS inode equivalents):
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@@ -359,7 +356,7 @@ another index for vnodes (AFS inode equivalents):
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&afs_volume_cache_index_def,
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&volume->vid, sizeof(volume->vid),
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NULL, 0,
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volume, true);
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volume, 0, true);
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======================
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@@ -375,7 +372,7 @@ the object definition should be something other than index type.
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&afs_vnode_cache_object_def,
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&key, sizeof(key),
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&aux, sizeof(aux),
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vnode, true);
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vnode, vnode->status.size, true);
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=================================
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@@ -393,7 +390,7 @@ it would be some other type of object such as a data file.
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&afs_xattr_cache_object_def,
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&xattr->name, strlen(xattr->name),
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NULL, 0,
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xattr, true);
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xattr, strlen(xattr->val), true);
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Miscellaneous objects might be used to store extended attributes or directory
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entries for example.
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@@ -410,8 +407,7 @@ cache to adjust its metadata for data tracking appropriately:
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int fscache_attr_changed(struct fscache_cookie *cookie);
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The cache will return -ENOBUFS if there is no backing cache or if there is no
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space to allocate any extra metadata required in the cache. The attributes
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will be accessed with the get_attr() cookie definition operation.
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space to allocate any extra metadata required in the cache.
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Note that attempts to read or write data pages in the cache over this size may
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be rebuffed with -ENOBUFS.
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@@ -536,12 +532,13 @@ written back to the cache:
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int fscache_write_page(struct fscache_cookie *cookie,
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struct page *page,
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loff_t object_size,
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gfp_t gfp);
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The cookie argument must specify a data file cookie, the page specified should
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contain the data to be written (and is also used to specify the page number),
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and the gfp argument is used to control how any memory allocations made are
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satisfied.
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object_size is the revised size of the object and the gfp argument is used to
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control how any memory allocations made are satisfied.
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The page must have first been read or allocated successfully and must not have
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been uncached before writing is performed.
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@@ -735,11 +732,11 @@ still possible to uncache pages and relinquish the cookie.
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The initial enablement state is set by fscache_acquire_cookie(), but the cookie
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can be enabled or disabled later. To disable a cookie, call:
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void fscache_disable_cookie(struct fscache_cookie *cookie,
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const void *aux_data,
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bool invalidate);
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If the cookie is not already disabled, this locks the cookie against other
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enable and disable ops, marks the cookie as being disabled, discards or
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invalidates any backing objects and waits for cessation of activity on any
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@@ -748,14 +745,15 @@ associated object before unlocking the cookie.
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All possible failures are handled internally. The caller should consider
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calling fscache_uncache_all_inode_pages() afterwards to make sure all page
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markings are cleared up.
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Cookies can be enabled or reenabled with:
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void fscache_enable_cookie(struct fscache_cookie *cookie,
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const void *aux_data,
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loff_t object_size,
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bool (*can_enable)(void *data),
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void *data)
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If the cookie is not already enabled, this locks the cookie against other
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enable and disable ops, invokes can_enable() and, if the cookie is not an index
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cookie, will begin the procedure of acquiring backing objects.
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@@ -766,6 +764,9 @@ ruling as to whether or not enablement should actually be permitted to begin.
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All possible failures are handled internally. The cookie will only be marked
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as enabled if provisional backing objects are allocated.
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The object's data size is updated from object_size and is passed to the
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->check_aux() function.
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In both cases, the cookie's auxiliary data buffer is updated from aux_data if
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that is non-NULL inside the enablement lock before proceeding.
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